Tuesday, 14 February 2017

Gender differences in risk-taking in pro basketball

One of the challenges of economics research is that you can't set up experiments. For instance, you can't easily randomly assign people to different treatments (e.g. gender) to see if or how their behaviour (or outcomes) are affected. Sure, you can run laboratory or field experiments, but then you wonder if the laboratory conditions affect the results and whether they hold in the 'real world'. Sports data provides an interesting solution to some of these issues, since they involve known rules and the incentives are usually pretty clear (most sports competitors are trying to win).

Which brings me to this IZA discussion paper from last year by René Böheim, Christoph Freudenthaler, and Mario Lackner (all from Johannes Kepler University Linz). In the paper, the authors use data from the NBA and WNBA playoffs from 2002-03 to 2013-14 to investigate whether there are differences in risk taking behaviour between men and women. This is an important question to investigate, since it may go some of the way towards explaining the gender wage gap, for instance. Risk-taking behaviour is notoriously difficult to observe, but in sports data it is readily apparent to the knowledgeable fan when a player is undertaking a high-risk strategy.

Specifically, Böheim et al. look at the probability that a player attempts a three-point shot in the closing minutes of a playoff game. A three-point shot is more risky than a standard two-point shot - it carries a higher reward (greater probability of winning, particularly if your team is down by two points), but a higher risk (since the probability of successfully sinking a three-pointer is less than for a two-pointer). They find that:
male teams increase their risk-taking towards the end of matches when they are trailing by a small amount and a successful risky strategy could secure the winning of the match. Our key finding shows that female teams, in contrast, reduce their risk-taking in these situations. The less time left in a match, the larger is the gap. A detailed investigation shows however that this difference is the result of risk-taking in matches where the costs of an unsuccessful risky strategy are relatively lower. In situations where the costs of an unsuccessful risky strategy are large - losing the match and, in consequence, the round in the elimination tournament - we find no difference in risk-taking between male and female teams. One potential explanation for our results might be male overcon fidence. If this were the reason for our findings, we would expect to observe a lower probability to throw successfully or to win the match. We do not find such evidence.
The results are interesting, but I don't fully buy their interpretation. To get more specific, they found that male teams increase their risk-taking (i.e. they attempt more three-pointers) when they are behind in the game (by up to two points), but this effect is only present when the team is ahead or tied in the playoff series overall. A team that is trailing in the playoff series (e.g. down 1-2 in a best-of-seven NBA finals series) does not engage in significantly more risk taking when down by one or two points.

My prior here would be that teams that are trailing in the series would be more likely to throw caution to the wind in an attempt to catch up, but Böheim et al. find the opposite (but only for men). The authors put this finding down to the costs of an unsuccessful risky strategy being lower (for those teams that are leading or tied in the series, compared with those who are trailing). However, I would expect that the benefits of the risky strategy are also lower (for teams that are leading or tied in the series), so there isn't a clear theoretical case for their interpretation (although the empirical case is that the risk-reward is positive for teams that are ahead in the series).

An alternative explanation may be to do with the difference in the cost-benefit calculation for the individual player versus the team. If your team is ahead in the series, then the series MVP is more likely to come from your team, so running up your personal score carries a high individual benefit (in addition to the team's benefit), whereas the cost is borne mostly by the team since no one will remember the three-pointers you missed when your team was ahead in the series. On the other hand, if your team is behind in the series and you undertake the risky strategy of attempting three-pointers, both the benefits (the fans remember you as the guy who got them back into the series) and the costs (the fans may remember you as the guy who wasted all those scoring opportunities by putting up crazy three-point attempts) fall on the individual. So, overall the benefit-cost calculation tends towards more risky strategies by the individual player if the team is ahead in the series.

But only for men. Is that because women are more team-oriented, so the difference in individual vs. team costs and benefits is less important? Or perhaps the monetary and status rewards for being a series MVP are greater in the NBA than the WNBA? Men may take more risks, but the key question of why is hardly settled.

Bonus video clip (this sort of shot wasn't included in the dataset, as there is little in the way of strategy when it comes to buzzer beaters; and yes, I know it's not pro basketball, but it is cool nonetheless):



[HT: Marginal Revolution, back in July last year]

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