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The Risks of Avoiding a Debate on Gender Differences

by Moshe Hoffman, Postdoctoral Scholar, and Erez Yoeli, Lecturer

Men are more likely to own risky stocks. They are more likely to choose competitive careers. And they are more likely to bargain aggressively for their starting salaries. The evidence is overwhelming: In virtually every setting ever studied – in laboratory experiments where people choose between gambles and empirical studies where retirement funds or career choices are analyzed – men take more risk than women.1,2

We know, we know. All of us are brought up to believe that men and women are the same, and we want them to be the same. But at least when it comes to taking risk, men and women are not the same.

This is not to say men are better. On the contrary, taking risk can be quite stupid. Men may own more stocks, but they are also more likely to die in a car accident while speeding in the Ferrari they bought with their stock-market earnings. They may choose competitive careers, only to find themselves paralyzed pursuing their ridiculously competitive hobbies. But risk does come with rewards: Stocks have higher average returns than bonds, and competitive jobs can be quite lucrative. These rewards make gender differences in risk preferences one of the pre-eminent causes of gender differences in the labor market, and these differences are enormous: Despite their higher likelihood of attending college or receiving an MBA, women still make 77 cents to the male dollar, make up 4.2 percent of CEOs at Fortune 500 firms, and are only 19 percent of the STEM (science, technology, engineering, and mathematics) workforce, and as you already know if you are reading this article, fewer women get MBAs.3,4,5,6

That’s it? So we can fix labor market disparities by merely training women to be as risk-taking as men? That’s great! Bring the girls to the boxing match; take them to see James Bond movies. Hell, take ’em to Vegas. We will close the wage gap by Easter, or at least by the time we have socialized a new generation of women at the blackjack table.

Well perhaps not quite by Easter, and perhaps not at all. What if women are just inherently more level-headed than men? Could it be?

Yes. For starters, humans certainly would not be the only species for whom that is true. Indeed, it turns out males take more risk than females in nearly every sexually reproducing animal. Male ants, male deer, and male baboons – they are all more likely to risk life and limb to procure resources such as food or mates than their level-headed female counterparts. There is a good evolutionary reason for that: Males have more to gain and less to lose from risky behavior. Namely, when males take on extra risk in foraging for food, ousting rivals, and fighting over territory, they are rewarded with dozens, even hundreds of mates, and many, many babies. A worthwhile gamble! Not so for the females. Those females who take the same risks do not benefit as much from the increased mating opportunities, as they are more limited in the number of babies they can have. One more? Two more? Not worth the gamble.6,7,8,9

The evidence for this theory is strong and growing stronger. In animals, we see sex differences in risk preferences covary with the degree of polygyny and reverse in species where males invest more in parenting. Anything to the contrary would have refuted the theory – but the evidence from animals lines up perfectly. What about us humans? Well, the evidence is there for humans, too: There is a strong correlation between various risk preferences and various measures of testosterone at various stages of development, including measures that are fixed at birth, before socialization could play a role; again, the opposite result would have refuted the theory, but we found exactly what one would expect if sex differences have an evolutionary basis.10,11

Are you kidding? You cannot be serious with all this talk of sex differences and evolution? Didn’t you hear about Larry Summers?

Oh, believe us, we know, and we do not blame you for being concerned. It makes sense to be wary of combining evolution with any kind of group difference, such as differences between men and women, because historically these were used to discriminate against some groups, in some cases leading to horrific treatment. But unlike, say, the Nazis, we are not using evolution to argue that one group is better than the other. We have not said that men evolved to be better because they take more risk or even that they have evolved to be better at assessing risk. We have argued they have evolved to like taking risk more. This is about preferences, not abilities. With caution, by incorporating what we know about evolution, we can hopefully address feminist issues in a scientifically sound and constructive manner.

How so? If natural selection has something to do with sex differences in risk preferences, then socializing boys and girls the same is unlikely to obliterate the differences in risk preferences, let alone wipe out the wage gap or shatter the glass ceiling. Even with equal socialization, we would expect men to prefer gambles and have higher wages. In fact, differential socialization may very well be a consequence of boys and girls being different, not the cause. Perhaps parents and teachers and TV producers are responding to sex differences, not creating them; telling them to treat boys and girls the same amounts to pressuring boys and girls to act against their instincts.12

Instead, perhaps, what we ought to be doing – those of us who care to reduce gender differences in the labor market and wish to harness our knowledge of the role of evolution – is evaluating labor market practices to make sure they do not needlessly reward risk-taking. Is it a coincidence that up-or-out promotion structures, which disparately and negatively impact women because of natural differences in risk preferences, are ubiquitous in precisely those fields in which women’s scarcity is lamented, for example, law firms, academia, and the military? Why does UC San Diego make pay increases contingent on obtaining outside offers? Why do firms make promotions contingent on management of one large project rather than success on a series of smaller ones? Are these policies worth the inadvertent sexism they cause? Is there no alternative? These are the questions we need to ask if we wish to close the wage gap and shatter the glass ceiling. It’s time we acknowledged inherent differences between men and women and used our understanding to improve the labor market for everyone.

Moshe Hoffman is a postdoctoral scholar in the computer science department at UC San Diego and a visiting scholar at the Program for Evolutionary Dynamics at Harvard University. His research primarily uses evolution to explain social behavior.

Erez Yoeli is an economist at the Federal Trade Commission, a lecturer at the Rady School of Management, and a visiting scholar at the Program for Evolutionary Dynamics at Harvard University. His research focuses on fraud and altruism.



  1. Croson, Rachel, and Uri Gneezy. 2009. “Gender Differences in Preferences.” Journal of Economic Literature 47: 448-474. Accessed January 6, 2013.
  2. Babcock, Linda, and Sara Laschever. 2003. Women don’t ask: negotiation and the gender divide. Princeton, New Jersey: Princeton University Press.
  3. Congressional Commission on the Advancement of Women and Minorities in Science, Engineering, and Technology Development. 2001. “Land of Plenty: Diversity as America’s Competitive Edge in Science, Engineering and Technology.” Report of the Congressional Commission on the Advancement of Women and Minorities in Science, Engineering, and Technology Development. 2000/cawmset0409/cawmset_0409.pdf.
  4. Allum, J.R., Bell, N.E., Sowell, R.S. 2012. “Graduate Enrollment and Degrees: 2001 to 2011.” Washington, D.C.: Council of Graduate Schools.
  5. Bertrand, Marianne. 2009. “CEOs.” Annual Review of Economics 1: 121-150.
  6. Wikipedia. “Women CEOs of the Fortune 500.” Accessed on January 12, 2012.
  7. Trivers, Robert L. “Parental Investment and Sexual Selection.” Sexual Selection and the Descent of Man. Edited by B. Campbell. Chicago: Aldine, 1972.
  8. Daly, M. and Wilson, M. 2001. “Risk-taking, Intrasexual Competition, and Homicide.” Nebraska Symposium on Motivation 47: 1-36.
  9. Dekel, E. E. and S. Schochter. 1999. “On the Evolution of Attitudes Towards Risk in Winner Take-All Games.” Journal of Economic Theory 87: 125-143.
  10. Robson, Arthur. 1996. “The Evolution of Attitudes to Risk: Lottery Tickets and Relative Wealth.” Games and Economic Behavior 14: 190-207.
  11. Andersson, M., Sexual Selection. Princeton: Princeton University Press, 1994.
  12. Hoffman, M. and E. Yoeli. 2012. “The Evolutionary Basis of Sex Differences in Risk Preferences.” UCSD Working Paper.