_ ip~~~~~~~~~15 a5 k1
POLICY RESEARCH WORKING PAPER 2527
Is Inequality Bad Data on occupational choice
-:11 among return migrants in
for Business? Tunisia reveal that higher
inequality of wealth reduces
A Nonlinear Microeconomic Model the level of new business
activity. The effect is not large,
of Wealth Effects on Self-Employment however. Even dramatic
redistributions of wealth
Alice Mesnard would not provide much
Martin Ravallion stimulus to entrepreneurship.
The World Bank
Development Research Group
Poverty and Human Resources H
January 2001 if
I POL;CY REsEARCH WORKING PAPER 2527
Summary findings
It is widely assumed that pervasive credit market failures The aggregate number of business start-ups is an
mean that a person's current wealth is critical to whether increasing function of aggregate wealth but a decreasing
or not that person takes up opportunities to start a new function of wealth inequality.
business. In other words, at any given mean, the higher the
Mesnard and Ravallion show that inequality in initial inequality of wealth, the lower the rate of new
wealth can be either good or bad for the level of business start-ups, through the existence of diminishing
entrepreneurship in an economy, depending on how returns to capital given liquidity constraints. In this
diminishing returns to capital interact with borrowing sense, the results suggest that inequality is bad for
constraints at the microeconomic level. business-but the size of this effect is small.
They use nonparametric regression methods to study The findings do not constitute a case for public
wealth effects on business start-ups among migrants redistribution of wealth as a means of stimulating
returning to their home country, Tunisia. They include business activity. There should probably be more
controls for heterogeneity, with specification tests for the research on interventions to reduce liquidity constraints.
nonseparable effects with wealth and for selection bias.
There is no evidence of increasing returns at low
wealth.
This paper-a product of Poverty and Human Resources, Development Research Group-is part of a larger effort in the
group to understand how the distribution of wealth in an economy influences macroeconomic activity and occupational
structure. Copies of the paper are available free from the World Bank, 1818 H Street NW, Washington, DC 20433. Please
contact PatriciaSader, roomMC3-556, telephone 202-473-3902, fax 202-522-1153, email address psader@worldbank.org.
Policy Research Working Papers are also posted on the Web at www.worldbank.org/research/workingpapers. Martin
Ravallion may be contacted at mravallion@worldbank.org. January 2001. (28 pages)
7he Policy Research Working Paper Series disseminates the findings of work in progress to encourage the exchange of ideas about
developmnent issues. An objective of theseries is toget the findinzgs out quickly, even if the presentationts are less than fully polished. Th7e
papers carry the names of the authors and should be cited accordingly. The findings, interpretations, and conclusions expressed in this
paper are entirely those of the authors. They do not necessarily represent the view of the World Bank, its Executive Directors, or the
countries they represent.
Produced by the Policy Research Dissemination Center
Is Inequality Bad for Business?
A Nonlinear Microeconomic Model of Wealth Effects
on Self-Employment
Alice Mesnard Martin Ravallion'
ARQADE, University of Development Research Group, World Bank
Toulouse I and ARQADE, University of Toulouse 1
JEL:D31,M13
Keywords: Liquidity constraints, wealth inequality, entrepreneurship
These are the views of the authors, and need not reflect those of their employers including the World
Bank. For their comments on this paper the authors are grateful to Bruno Biais, Esther Duflo,
Emanuela Galasso and Dominique van de Walle.
1. Introduction
It is widely assumed in economic theory and policy that pervasive credit market failures
mean that a person's current wealth is critical to whether or not that person takes up
opportunities to start a new business. Support for this assumption has been found in empirical
evidence of significant current wealth effects on the probability of entering self-employment.2
The existence of liquidity constraints suggests that the level of aggregate wealth in an
economy will matter to the number of business start-ups. But will the distribution of that wealth
also matter? If in fact markets provide too little credit to support entrepreneurship, then there
may be a case for interventions that target extra credit to poor potential entrepreneurs.
Presumably this will be at the expense of less poor ones. The implications for the aggregate level
of new business activity thus depend critically on higher moments of the distribution of wealth
than its mean. It is known that the occupational structure of a credit-constrained economy
(including the extent of self-employment) can depend on the initial distribution of wealth
(Banerjee and Newman, 1993). There are also theories suggesting that asset inequality impedes
entrepreneurship and hence aggregate investment and macroeconomic growth.3
It is far from obvious on a priori grounds whether inequality is good or bad for the
aggregate level of business activity in an economy. The potential ambiguity in the relationship
between entrepreneurship and wealth distribution can be illustrated with a simple model depicted
in Figure 1 - which we derive more formally later in this paper. Liquidity constraints entail that
the probability of someone starting a new business (on the vertical axis) rises with personal
2 See Evans and Jovanovic (1989), Evans and Leighton (1989), Holtz-Eakin, Jouflaian and Rosen
(1994), Magnac and Robin (1996), Blanchflower and Oswald (1998), Paulson and Townsend (2000).
3 Models with this feature can be found in Benabou (1996), Piketty (1997), Aghion and Bolton (1997),
Aghion et al. (1999) and Banerjee and Duflo (2000).
2
wealth (horizontal). There is lumpiness in the capital requirements for setting up a new business.
It is difficult for someone with low wealth to finance any extra capital for a new business beyond
a modest personal endowment. Thus one can postulate that, at low wealth, there are increasing
returns from extra wealth in terms of one's ability to borrow extra resources; at low wealth the
relationship is convex. Above some point, the probability of starting a new business increases
more rapidly with wealth, but with diminishing returns to capital setting in, and borrowing
constraints starting to relax, such that the probability of a new start is a concave function of
initial wealth above some point. Such a model yields ambiguous predictions about the effects of
changes in wealth distribution on new business activity. Small mean-preserving redistributions
from anyone above the point of inflexion in Figure 1 to anyone below this point could either
increase or decrease the aggregate number of business starts in a fixed population.
Redistributions amongst those above (below) the critical minimum will increase (decrease) the
aggregate number of new starts.
What does the evidence suggest? Past micro empirical work on entrepreneurship has
given little explicit attention to distributional effects, though some specifications have allowed
for nonlinearities in the wealth effect on self-employment. For example, Evans and Jovanovic
(1989) included both linear and squared terms in current family wealth in their regressions for
the probability of entering self-employment amongst young US men. They found a negative
coefficient on squared wealth though it was not significant. (The linear and squared terms were
jointly significant.) There is also some empirical evidence from cross-country growth
regressions suggesting that initial inequality matters to the subsequent rate of growth, though it is
not clear what structural role entrepreneurship has played. Nor have the results in the literature
been robust to alternative specifications, and there are a number of concerns about both the data
3
and methods used. For example, spurious inequality effects in an aggregate growth regression
can arise from the assumptions made in aggregating across micro-relationships, given credit
market failures (Ravallion, 1998). The validity of the common assumption that initial inequality
has a linear effect on aggregate growth is also questionable (Banerjee and Duflo, 2000).4
This paper uses micro data to test whether inequality matters to the aggregate rate of new
business activity. We look for nonlinear wealth effects on the transition to self-employment,
consistent with the argument that the extent of aggregate business activity in an economy
depends on the distribution of wealth. The paper also tries to assess how sensitive the aggregate
level of new business activity is to changes in the distribution of wealth amongst potential
entrepreneurs.
We try to learn more about the implications of wealth distribution for aggregate
entrepreneurship by studying the empirical relationship between starting a business and the
amount of accumulated savings brought back by return migrants in a developing country. Return
migrants provide an interesting sample for the purpose of studying wealth effects on
entrepreneurship. The problem of unexploited opportunities for taking up new business activities
is often assumed to be greater in developing countries, where capital markets are thought to be
less effective, though it might also be conjectured that start-up costs are lower in developing
countries. One must expect heterogeneity in other factors relevant to occupational choice in a
4 Mention should also be made of measurement error in both the levels and changes in income
inequality in cross-country data sets, including comparability problems between countries and over
time arising from survey error (sampling and non-sampling) and heterogeneity in survey design and
processing (see, for example, Atkinson and Brandolini, 1999). One expects that this will matter more
to tests which allow for country fixed effects than standard growth regressions, since the signal-to-
noise ratio could well be quite low for changes in measured inequality in existing data sets.
4
developing country, as elsewhere. In this respect, return migrants are likely to be a more
homogeneous group than the population as a whole within a developing country.
However, the main attraction to studying return migrants is that they offer the hope of
avoiding a common problem in using ordinary survey data for this purpose, namely that wealth
immediately prior to the time of taking up self employment is unobserved. Wealth data are
uncommon, and even when available it is obtained at the survey date, typically after the
occupational choice has been made. By contrast, migrants have returned to their home country
with diverse amounts of wealth, accumulated from past savings while abroad, and then face the
choice of what to do. By asking how much was accumulated while abroad, and seeing which
ones started up a new business on their return, we can hopefully identify the wealth effects on
entrepreneurship, and test for nonlinearity.
In terms of our method of analysis, our main point of departure from the past empirical
work on entrepreneurship is that we do not parameterize the relationship between start-up wealth
and entrepreneurship. With liquidity constraints, there is no obvious reason why the wealth effect
on occupational choice would be linear, or indeed have any specific parametric form. If there are
fixed start-up costs and the liquidity constraint takes the form of a collateral requirement for
borrowing then one would expect the effect to be highly nonlinear, at least amongst
observationally identical workers. Only when own wealth reaches some critical level
(conditional on individual characteristics) will new businesses emerge. We build this feature into
a model of business start-ups, in which the curvature of the entrepreneurship-wealth relationship
emerges from the balancing of opposing effects stemming from diminishing returns to capital
versus borrowing constraints. Motivated by this theoretical model, we treat the wealth effect in a
5
flexible way, to see if it exhibits the features one would expect if distribution matters. To achieve
this flexibility we employ non-parametric regression methods.
We also allow for heterogeneity in other characteristics in the form of linear controls.
Thus we apply recent advances in the estimation of partial linear models (as reviewed by
Yatchew, 1998). We extend this approach by also allowing for the possibility that individual
characteristics influence new business starts in a non-separable way. This could happen if credit
markets work better for some people than others. For example, wealth may be less of a constraint
on starting a business for well-educated entrepreneurs. This calls for a new specification test for
partial linear models. The inherent nonlinearity of liquidity constraints permits identification for
the purpose of specification testing.
The following section discusses the relationship between business start-ups and wealth in
general terms, while section 3 outlines our econometric model. Section 4 describes the data and
gives some descriptive results. The estimations are presented in section 5, while section 6
examines their implications for the question in our title. Section 7 concludes.
2. Wealth effects on entrepreneurship in theory
We assume that a given amount of accumulated savings W allows one to borrow up to
some amount of start-up capital K. In the Evans-Jovanovic (1989) model K is some fixed
multiple of W with slope not less than unity. We allow an increasing slope arising from
limitations on borrowing facing the poor, as in Figure 2. More precisely, we let K be some
unknown but strictly increasing and convex function of W:
Ki =e(W, ) for W1 E [W min, W ma ] (1)
6
where t(W ) > Wi, q'> 0, 0" > 0. This assumption characterizes what one would expect to find if
poor entrepreneurs have very little access to credit, but borrowing becomes progressively easier
(though still credit-constrained) at higher levels of wealth.
The output from the new business is F(Ki) where the function F is increasing and
concave as usual. (Both the functions qi and F are taken to have continuous derivatives up to at
least the second order.) There is some fixed own-labor requirement that is subsumed in the
function F. The opportunity cost of capital is r while for own labor it is wi which is a random
variable with continuous twice differentiable distribution function T1. (Note that w; could also
include random differences in outputs.)
The probability of starting a new business (Pi ) is then the probability that
F(O(W,)) - ro(Wj) exceeds wi, as given by:
Pi = T[F(O(W,)) - ro(fW)] = f(W;) (2)
with slope:
f'(Wi) = T' (.)[F'(Ki) - r]qY(Wj) (3)
This vanishes in the special case in which the entrepreneur is not liquidity constrained, and so
can employ as much capital as desired (F' (K1) = r). In the liquidity-constrained case, however,
f' (W) > 0.
The curvature of the functionf is less obvious. In the special case in which the
distribution of w is uniform (T' (.) is constant) and the capital stock is directly proportional to
initial wealth (as assumed in the Evans-Jovanovic model), the functionfwill be strictly concave,
with second derivative:
7
f" (WK ) = T' (.)b' (Wi )2 F" (Ki) < 0 (4)
However, this is only one possibility. Allowing for a non-uniform distribution of the
opportunity cost of labor, and relaxing the assumption that capital is proportional to wealth we
have:
f" (Wi) T' (.)[O(Wi)2 F"(K,) + (F'(Ki) - r)b" (W,)] + TI (.)(F' (K0) - r)2 0 (Wi)2 (5)
It is evident from (5) that the curvature of the functionf is ambiguous. There is a concave effect
coming from diminishing returns to capital (0' (Wi )2 F" (K, ) < 0 ), a convex effect from the
borrowing constraint (F' (Ki ) - r)b" (W, ) > 0 ) and a third term of unknown sign coming from
any non-uniformity in the distribution of the opportunity cost of labor. Sufficient conditions to
obtain the pattern in Figure 1 are that:
(i) f '(Wi ) <0 ; this will hold if (for example) the functions F and 0 are quadratic, and
the distribution of labor cost is uniform,
(ii) diminishing returns to capital do not set in until wealth reaches some critical
positive level, so F" [b(W min )] = 0,
(iii) credit constraints cease to bind at sufficiently high wealth, implying that
F' [>" (W m )] = r.
(iv) the distribution of the opportunity cost of labor is either uniform or unimodal with a
rising density at low wealth ('T" [F(b(W mrin)) - ro(W min)] > 0) and falling at high wealth
(T" [F(b(W m))-ro(W max )] < 0).
8
Together these conditions assure that f " (W mi) > 0 and f " (Wm) < 0 . Thus, by continuity of
f" (Wi ), there exists a unique point of inflection at which the relationship switches from being
convex at low wealth to concave, as in Figure 1.
The aggregate number of new business start-ups is
n
P = P(WI, W2v ..... Wn) = If(W;) ......... (6)
i=l
If the functionfis strictly convex (concave) then the function P will be strictly quasi-convex
(concave) in the vector of wealth endowments, (Wl ,W2 ,...W") . If one is comparing two
distributions of wealth, one of which can be obtained from the other by a mean-preserving
spread, then it follows from well-known properties of concave functions that the distribution
with higher inequality will generate a higher (lower) aggregate number of new business starts if
the functionfis convex (concave).
In this model, the effect of wealth distribution on the aggregate number of business starts
is theoretically ambiguous. Inequality amongst those with wealth above the point of inflexion in
Figure 1 will reduce aggregate business activity; inequality amongst those with wealth less than
this value will be good for business activity. Nothing in general can be said about redistributions
from those above this point to those below it. Next we outline our method for studying the issue
empirically.
3. An empirical model
The discussion in the last section points to the need to represent the initial wealth effect
on entrepreneurship in as flexible a way as possible, for which non-parametric regression
methods are an obvious choice.
9
To take such a model to data we must allow for heterogeneity in other characteristics
besides start-up wealth. This could arise from differences in output at a given level of capital
(such as due to differences in the availability of family labor to help with the business) or
differences in the opportunity cost of labor. We use linear controls, so that our method entails
estimating partial linear regressions, in which the sub-function for the wealth effect is nonlinear.
However, we introduce a specification test, which allows us to relax this assumption. In
particular, the test allows for control variables to also enter non-separably, through the wealth
effect.
Thus we write the probability of starting a business as some unknown function of W, as
well as control variables X:
PiE = f(Wi ) +Xj-r +V i (i =1,..., n) (7)
in which the zero-mean innovation error has variance U2 . Notice that, unlike a probit or logit
model, there is no guarantee that the predicted values for P will lie entirely within the (0,1)
interval. We will check if our estimates satisfy this condition.
All that we assume about the functionf is that it is smooth and single valued; in
particular, the first derivatives off are bounded by constants, k > lAf (Wi )I /)AW1 I. The function
need not be monotonic, or take any parametric form.
To estimate the model of business starts in (7) we follow the literature on partial linear
models. Following Robinson (1988) we order all observations in terms of their values of W, and
take differences between the data for successive ranked observations, giving the regression:
AP, = Af (W,) + AXi 7r + AV v (8)
10
where AXi is the difference between the value of X for the i'th observation and that for i-I when
ranked in ascending order of W. Under our assumption about the functionf, the first term on the
RHS vanishes as n goes to infinity (plim[f(Wi) -f(Wi>.)] = O). So we estimate the following
parametric regression by least squares:
APi = AXi r + A v i (9)
This gives us consistent estimates of the ir parameters under standard assumptions. We can then
estimate the non-parametric regression:
Pi -Xi k= f(W,)+v, (10)
Higher-order differencing achieves efficiency gains in this method (Yatchew, 1998). We
write equation (9) as:
m m m
, d1jPij = ( E d1jXi-j ) + E_ (d1 1 )
j=O = j=O
where the differencing coefficients satisfy:
m
I dj =0 (12)
j=0
(which allows us to drop the non-parametric effect from equation I 1) and the normalization
condition:
Ed. =1 (13)
j=0
(which assures that the transformed residuals have variance a2). Hall et al., (1990) provide the
optimal weights up to m=1 0.
The formulation in (1) follows the literature in assuming that start-up capital is solely a
function of wealth (though we relax the assumption that it is a constant proportion of wealth). A
11
more general specification allows characteristics to influence start-up capital independently of
wealth. For example, it may be conjectured that better education allows a worker to borrow more
at given wealth. In terms of the model in section 2, individual characteristics might enter either
the qi function or through differences in r. To allow this we consider the model:
Pi = f(W1 +Xjy)+X,w +vi (14)
To test this against (7) we take a first-order Taylor series expansion of thef function:
f(Wi + Xiy) = f(Wi) + fw (Wi )Xiy + residual (15)
where fw denotes the first derivative off. So by adding an interaction effect between X and the
estimated slopes of thef functions as an additional regressor we can test whether y = 0. Under
the null hypothesis (r = 0) we should find that the estimated parameters of the following
regression are jointly insignificant:
Pi -Xii-fK(W,)=fW(W1)XiY±vE (16)
This supplementary regression thus provides a specification test for our model.5
4. Data and descriptive statistics
The survey we use here was done in 1989 by the Tunisian Settled Abroad Office in the
Foreign Affairs Ministry, with the collaboration of the Arabic League. The survey was done in
all geographical areas of Tunisia (both rural and urban areas). Return migrants are defined as
5 We have not seen this test in the literature, and one expects that there would be other application in
which this test would be of interest.
12
workers who have migrated abroad at least once during 1974-86.6 This group was over-sampled
to get more observations.7
The non-migrant sample suggests only a weak correlation between wealth and self-
employment. In the data we can measure the wealth accumulated up to 1986. The mean wealth
of those who became self-employed between 1974 and 1986 is 689 dinars, while it is 454 for
those who did not. However, the difference is not statistically significant (a t-test gives 1.62). If
we restrict the sample to the workers who were not self-employed in 1974, the difference
between the mean wealth accumulated up to 1986 by self-employed (equal to 689 dinars) and by
salaried workers (397 dinars) becomes significant (with a t-test of 2.02).
However, it may well be hard to detect the impact of credit-constraints in the non-migrant
sample. We know whether someone is self-employed at the date of interview, or has been so.
And we know wealth accumulation up to the interview date. However, there are obvious
concerns about the endogeneity of wealth to self-employment in a sample of non-migrants. There
is also likely to be considerable heterogeneity in other characteristics that cloud and possibly bias
the comparison.
In this paper we focus instead on the sub-sample of returned migrants. Returning from a
long period overseas makes a natural break in work history. For such migrants we can measure
the probability of self-employment after returning to the home country. And we can identify how
much money they brought back from their period overseas, which is pre-determined at the time
they make their decision about what work to do on return. This group is also more homogeneous
6 1974 is of some significance since political and economic changes in that year made out-migration
towards European countries (the traditional host countries for Tunisian workers) more difficult for
most Tunisians.
7 See Mesnard (1999, pp. 205-211) for a more detailed description of the survey.
13
than the population at large, which should also make it easier to detect any relationship between
wealth and occupation choice.
The return migrants can be thought of as a sample selected from a set of migrants, not all
of which returned. The sample selection process is unknown and we have no data on those who
did not return. It is plausible that the probability of returning depends positively on accumulated
wealth. Then the wealth effects we see in the data on return migrants also include an unknown
selection effect, as well as liquidity constraints.
This does not appear to be a serious concern for the problem at hand. We want to know
how important wealth distribution within the home country is to the level of business activity in
that country. Since we want to condition on residence in the home country, we need not be
concerned about the possibility that return migrants are untypical of migrants that did not return.
Another possible selection bias is more worrying, however. Return migrants may not be
typical of the workforce as a whole in the country they return to. This we can test for, using data
from the sample of non-migrants. We discuss the details later.
Our main sample covers 1224 male returned migrants who intend to stay indefinitely in
Tunisia.8 The survey obtained general information about their migration history (number of
migrations, dates, locations, return motives, duration, employment) and their working and living
conditions during their last migration. To identify new business starts in the data we build a
dummy variable equal to one if a worker is self-employed after return and was not self-employed
before migrating and equal to zero otherwise. There is comprehensive information on the assets
accumulated during their migration. The survey obtained data on a number of obvious control
variables, including age and education. Whether one takes up self-employment is also likely to
8 We dropped 102 migrants who are temporarily visiting Tunisia for vacation, as well as 12 women.
14
be correlated with where one lives, as an influence on proximity to markets. However,
endogeneity concerns speak against controlling for current location in this context (given that
return migrants can in principle choose where to return to). We do include, however, controls
for place of birth.
Table 1 provides summary statistics. Column (1) gives data on the sub-sample who had
not been self-employed prior to migrating but took up self-employment on return. Column (2)
gives data for those who had not been self-employed, and did not take this up on return. Column
(3) covers those who had been self-employed previously and those who are salaried on return.
The sub-samples differ in most respects. However, the most striking difference is that
workers who take up self-employment after return have accumulated much larger savings (1086
dinars) on average when they were abroad than other workers of the restricted sample who are
salaried after return (442 dinars) or than other workers from the full sample (466 dinars).
From the data we also find that those who took up self-employment mainly use their own
capital for investment after return: 87.6% of projects are realized with savings accumulated
during migration and only 12.4% of migrants received extra funds from special programs
(Mesnard, 1999). None of them relied on formal bank credit, though some informal credit was
probably available. They explicitly mention their difficulties in getting access to credit markets
when asked about the main obstacles faced in starting up their projects.
5. Estimation results
Since we are interested in whether a return migrant enters self-employment we restrict the
sample to those who had not previously been self-employed prior to their migration. Table 2
gives the estimated parameters on the control variables. For the distributed lag we set m= 10 in
equation (11), although the results were quite similar with m=1.
15
The control variables are jointly significant, though only a couple of variables are
individually significant. Married respondents were less likely to start a new business; those born
in the Center-East of Tunisia were more likely to do so. Individual enterprises have flourished in
the Center-East region around Sousse, whose inhabitants are relatively mobile and have created
networks with migrants working in France, Italy or Germany. The specification test for our
model shows that individual characteristics such that education levels do not interact with wealth
to affect entrepreneurship. When they influence the decision to start up businesses, they do so
independently of wealth. We also estimated the model on the full sample (including those who
had been self-employed prior to migrating); the results were very similar.
Figure 3(a) gives the nonparametric regression of P, - Xi * i on wealth. We use the local
regression (LOWESS) method of Cleveland (1979).9 The relationship is increasing and at least
weakly concave over the whole range of the data. When we calculate the predicted probabilities
we find that almost all (94%) of the sample is within the (0,1) interval; 6% of the predicted
probabilities are negative, and none are above one. Figure 3(b) gives the corresponding
regressions without the control variables. We also estimated these regressions without restricting
the sample to those who had not been self-employed prior to migrating; the results were very
similar to Figure 3.
To test for selection bias in our results we pooled the return migrants with other non-
migrant workers and estimated a probit in which the dependent variable took the value one if an
observation was in the return migrant sample and zero otherwise. We then included the inverse
Mills's ratio from this probit as one of the control variables in the vector X. The wealth variable
9 This is closely related to Fan's (1992) method, which has advantages over kernel regression given
the uneven spacing of the wealth data at extremes; for further discussion see Fan (1992) and Deaton
(1997).
16
entered linearly in logs in the probit. While the model is identified on nonlinearity, we also used
an instrument comprising a dummy variable for whether the worker was older than 18 in 1974.
Our idea here is that reaching adulthood in 1974 creates a discontinuity in the probability of
migrating after that date but does not affect the probability of starting a new business on return.
Otherwise the control variables in X were the same.'0 The probit revealed a number of significant
factors in explaining who was a return migrant in the sample, and log wealth, X and the
instrument were jointly significant at better than the 0.00005 level."
However, we found no evidence of selection bias in our main model of business start-ups.
The Mill's ratio from the first stage probit was insignificant as an additional control variable; the
t-test was 0.239 (0.395 if we drop the dummy for having reached adulthood in 1974 out of the
selection equation). So this does not suggest that we need be concerned about selection bias in
our estimates of the wealth effect on self-employment. Recall, however, that we cannot rule out
selection bias with respect to migrants as a whole, since we do not have data on those that did not
return to Tunisia.
We find no evidence of a low-level convexity. The curve is concave for low wealth
levels, then becomes more linear for higher values. Adding control variables attenuates slightly
the slope of the curve. But the relationship is very similar without controls.
This lack of any sign of non-convexity at low wealth does not contradict the model in
section 2. Our results suggest that people can start up a business with relatively little capital.
There may still be increasing returns to own wealth as collateral, but this is swamped by the
0 One minor difference is that we used age in 1986 instead of age at the date of return, for consistency
across the samples.
The significant variables at the 5% level were log wealth (positive), the instrument (positive), age
squared (negative), no education, secondary and higher education level (negative, relative to
primary), number of dependents (positive), and being born in the center west or south east (positive).
17
decreasing returns effect in production (recalling equation 5). Latent heterogeneity in the
borrowing constraint or production functions could also hide the convexity at low wealth. For
example, suppose that a bank can observe indicators of the likely effort of borrowers and adjusts
its collateral requirements accordingly. Then on aggregating across the diversef functions in
estimating the regression one could lose all sign of the convexity at low wealth.
6. Implications
To help interpret our results, we can estimate the contribution of wealth inequality to the
average rate of business starts amongst return migrants. This is given by:
n n
A -_ f (W,W /n) -If(W,) /n (17)
i=I i=]
which is positive forf concave. Using the empirical non-parametric regression function the value
of A is 4% points. With complete equalization of wealth, the predicted rate of new business
starts at mean values of the controls is 23.92%, as compared to a predicted mean on the same
sample of 19.85%. This must be judged a modest impact given the extent of the wealth
redistribution.
A smaller redistribution naturally gives an even lower impact. Suppose that a
redistributive wealth tax is introduced. The individual tax rate is an increasing function of initial
wealth levels, and is budget neutral i.e.,
t, = T I/W, = a +,fW, (18)
where,f > 0. When the value of a is set to assure that YT =0 we have:
ti =xw , - MSW / W) (19)
18
where MSW= 2I n is mean squared wealth and W is mean wealth. The value of ,8
determines how much redistribution is achieved. To interpret /3 suppose that the pattern of
taxes and subsidies given by (19) entails tax rate, t on the richest person in the sample, with
wealth W*. Then
1 * t (20)
W*- MSW I
Using the estimated (individual-specific) first derivatives off we can estimate the change in the
probability of starting a new business for each individual. Adding up these probability changes,
we then have a measure of how sensitive the aggregate level of business activity is to the
distribution of wealth. (This is not of course a policy simulation; rather it is a means of assessing
how responsive the overall rate of business starts is to changes in inequality.)
Table 3 gives the percentage changes in the number of new business starts for various
wealth redistributions, as indicated by the mean tax rate on the richest individual. As one would
expect, the impact on the aggregate number of new business starts rises with the extent of the
redistribution. However, the effect of tax-subsidy scheme entailing even a 50% tax on the richest
wealth-holder only increases the average rate of new business start ups amongst return migrants
by 0.61% points.
7. Conclusions
We have studied one aspect of the theoretical arguments that have been made linking the
composition of economic activity to the distribution of wealth, given credit-market failures. The
distribution-dependence of aggregate business activity is theoretically ambiguous in our model.
On the one hand, diminishing returns to capital will tend to mean that wealth inequality is bad for
the aggregate number of business start-ups at any given mean wealth in the economy. On the
19
other hand, increasing returns to initial wealth (as the collateral for borrowing to augment initial
wealth in capital formation) will tend to mean that inequality is good for aggregate business
activity. The outcome is an empirical question.
Rather than impose a specific functional form on the data we have used flexible
nonparametric methods to study the empirical relationship between initial wealth and new
business start ups. In the hope of better identifying the relationship, we have focused solely on
return migrants who have brought back diverse amounts of accumulated savings from their
period abroad, and can be expected to be contemplating whether to take up self-employment on
returning to their home country.
Our data for Tunisia on new business starts amongst return migrants are consistent with
the existence of liquidity constraints on entrepreneurship. We cannot rule out the possibility that
wealth is picking up ability differences correlated with wealth, though we do control for obvious
ability correlates, such as education. Amongst the variables we have in our data set, wealth
appears to be of over-riding importance to whether or not a return migrants starts a new business.
We do not find evidence of a low-level convexity, as one would expect if there were
increasing returns to wealth as collateral. The wealth relationship is increasing and at least
weakly concave over the range of the data. This suggests that in this setting it is possible to start
some sort of business with very little wealth, and that the non-concave borrowing constraint in
our theoretical model does not come into play in practice. Start-up capital is some constant
multiple of wealth; probably wealth itself in most cases. This is consistent with the fact that none
of those interviewed indicated that they had relied on formal credit sources.
These results implies that, at any given mean, the higher the initial inequality of wealth,
the lower the overall rate of new business start-ups, through the existence of diminishing returns
20
to capital. In this sense, our results suggest that inequality is bad for business. However, the
quantitative magnitude of this effect is small. Even full equalization of wealth at the same mean
would only increase the rate of new business starts amongst return migrants from 20% to 24%.
Less redistribution will naturally have less impact. A progressive redistribution entailing a tax
rate that rises with wealth, reaching 50% for the richest person, would increase the rate of new
business starts by less than one percentage point.
Our findings do not constitute a case for public redistribution of wealth as a means of
stimulating business activity. The maximum impact appears to be modest. Nor can we rule out
the possibility that the nonlinear wealth effects on self-employment arise from other factors than
liquidity constraints; if so, then pro-poor redistribution of wealth may do nothing for the level of
new business activity. And even if liquidity constraints are the whole story, if the wealth
redistribution entails changing other factors influencing business activity (such as prices or
access to markets for outputs and inputs) then the effect is ambiguous. Further research in testing
for liquidity constraints and in studying specific interventions will hopefully provide a deeper
understanding of the policy implications.
21
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23
Figure 1: Stylized relationship between entrepreneurship and wealth
Probability of
new business
start (P)
Initial wealth (W)
Figure 2: Borrowing constraint
Capital stock
available
(K) 0(W) K= W
Initial wealth (W)
24
Figure 3: New business starts and initial wealth
(a) With controls
Lowess smoother, bandwidth = .8
0
Atceo00o00 0o 0 0
;;~~~~~~~~ /
0~~~~~~
0~~~~~
.5
0 5000 10000
Epatrim
(b) Without controls
Lowess smoother, bandwidth = .8
1 .02415 -00 0 00 oooo0
0)~ ~~~~
0 X , o 0 00 0 0 0 0 0
4 1 0850
patrim
2s
Table 1: Descriptive statistics
Not previously self-employed
(1) (2) (3) (4)
Took up self- Others Rest of full Total sample
employment (n=840) sample (n= 1224)
(n=210) (n=1014)
Age at return 34.87 32.44 33.66 33.87
(10.60) (10.66) (0.38) (11.13)
No education (%) 36 33 38 38
Primary school (%) 46 50 46 46
Short secondary school (%) 4 5 4 4
Long secondary school (%) 13 12 11 12
Number of dependents 5 4.55 4.79 4.82
(2.94) (2.93) (2.96) (2.96)
Married (%) 81 80 82 82
Born in area of Tunis (%) 5 5 4 5
Born in Center East (%) 23 19 21 21
Born in Center West (%) 21 24 24 24
Born in Southern East (%) 16 23* 22* 21
Born in Southern West (%) 10 11 10 10
Born in Northern East (%) 8 6 6 6
Born in Northern West (%) 17 13 13 13
Savings at return 1086.2 442.35* 465.9* 580.10
(1539.13) (951.77) (926.45) (1091.94)
(* significantly different from the mean in column (1), t-test)
26
Table 2: Parameters on control variables in explaining the probability
of starting a business amongst return migrants
Coefficient
(t-ratio)
age at return 0.011
(1.84)
age squared 0.000
(1.5)
no education 0.053
(1.2)
short secondary school -0.103
(1.17)
long secondary school -0.021
(0.43)
married -0.133
(2.96)**
number of dependents 0.003
(0.40)
born in Center East 0.107
(1.88)*
born in Center West -0.009
(-0.18)
born in Northern East -0.003
(0.05)
born in Northern West 0.013
(0.22)
born in South East -0.067
(1.28)
born in area of Tunis -0.07
(0.94)
Constant -0.002
(0.13)
Observations 695
R-squared 0.04
Tests of y = 0: F(13,869) 0.79
Prob=0.67
Note: Robust t-statistics in parentheses; one extreme value (savings=20550) dropped.
*significant at 5% level; ** significant at 1% level.
27
Table 3: Effects of wealth redistribution on the number of business start-ups
t* Absolute change % change
(% points) (P =19.85%)
5% 0.06 0.30
10% 0.12 0.60
25% 0.31 1.56
50% 0.61 3.07
Note: The table gives the predicted changes in the proportion of previously not self-employed return
migrants who take up self employment as a result of a progressive tax/subsidy scheme such that the
richest individual has a tax rate of t
28
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