to the treatments is a form of indirect reciprocity towards the employer, driven by the fact that
the employer has acted pro-socially by offering charitable donations as part of the compensation
package. We believe that if such an effect is present, it is of second order compared to the direct
effect of the donation appealing to the worker’s altruistic motivation toward the charity itself. To
see this note that a worker who is not altruistic would not derive any additional utility from the
donation made by the employer and therefore would not have any reason to reciprocate toward the
employer. Thus, any such type of indirect reciprocity is conditional on the worker being altruistically
motivated, implying that its effect on worker’s effort provision is of second order compared to the
direct effect of the worker’s own altruistic motivation, which this study aims to identify. Also, as
explained above with a piece rate compensation scheme in place, working harder is a very blunt
instrument to reciprocate toward the employer.
Another important finding of this paper is that there are considerable gender differences in
pro-social motivation. In particular, in our sample, pro-social behavior is displayed by women, but
not by men. This finding is consistent with the literature on gender differences in social preferences.
In particular, Eckel and Grossman (1998) report results from dictator experiments in conditions of
anonymity that indicate that women are more generous than men: women donate on average about
twice what men donate. Andreoni and Vesterlund (2001) also study gender differences in a dictator
game where the price of giving varies and find more nuanced results: women are more generous
when giving is expensive, and as giving becomes cheaper men are more altruistic. Mellstrom
and Johannesson (2008) carry out a field experiment to examine whether offering blood donors a
monetary compensation might crowd out their intrinsic motivation for giving and find this to be
the case for women but not for men.
The finding of a gender difference in pro-social behavior in a workplace setting may have impor-
tant implications for women’s economic outcomes, as if women are more likely to enter occupations
and sectors with characteristics that engender pro-social behavior, e.g. health, education and so-
cial care, and require less monetary compensation then gender differences in pro-social motivation
would help explain the observed occupational segregation by gender, that accounts for a substantial
portion of the overall gender earnings gap (Gunderson, 1989).
An important related issue is that of accounting for the sorting of workers that takes place in real
labor market settings. The importance of sorting when measuring social preferences experimentally
has been demonstrated by Lazear et al. (2006). Accounting for self-selection will not only lead to
the detection of the treatment effect for those workers who choose to sort into care-related jobs,
but also the identification of the characteristics that determine selection into sectors that engender
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