Is the Kuiper Prize Sexist?

On October 19, at the 48th annual meeting of the Division of Planetary Sciences, Patricia Knezek held a talk about implicit bias in astronomy. As part of the evidence for a bias against women, Knezek apparently offered the distribution of some of the major prizes given by DPS. Her slides are available online now, but James Tuttle Keane's tweet offers an excellent summary of the facts I would like to draw attention to in a single image:

"The Kuiper is particularly appalling," he remarks, which at first pass seems like a reasonable conclusion. Women make up 27% of the DPS members and only 3% of the Kuiper Prize winners.* Indeed, exactly one out of 32 winners has been a woman since the award was established in 1984, namely, Carle M. Pieters, who won in 2004.

But is this really as "appalling" as it seems? To understand why it may not be, you have to know something about the Kuiper Prize. Most importantly, it is a lifetime achievement award. (I have conferred with Dale Cruikshank, the historian of DPS and winner of the Kuiper in 2006, who has confirmed that this is a correct description of the award.) I checked the ages in a quasi-random sample of 10 of the 32 winners since 1984 and found that the average age was 67.2 years. Though there are some outliers, it seems clear that the award is given mainly to astronomers in their 60s. Carle Pieters, for example, won hers when she was 61.

Now, look at that graph in the bottom right-hand corner of Keane's image. Since about 10% of all astronomers were women in the mid-1980s, it seems highly unlikely to me that 27% of astronomers over 60 have been women since then, or even are now. Indeed, assuming that it takes about 30 years for an astronomer to gather a lifetime of achievements worthy of the award, the odds of a woman winning the Kuiper fair and square (i.e., unhindered by "implicit bias") will be contingent on the gender composition of the field, not in that year, but thirty years earlier. Presumably there were almost no female astronomers in 1954, so the chance that a woman would win in 1984 was essentially zero.

What about Pieters' win? If we follow the graph backwards to around 1974, it seems the chance that the winner would be a woman in 2004 was about 5%. That's pretty spooky, right? It took exactly twenty years for the first woman to win the prize 2004. That means that at the very time when 5% of the winners were women, there was also a 5% chance that a woman would win. I've tried to find some statistics to determine the proportion of astronomers over sixty who are women in any given year. So far I haven't had any luck. It is sure to be less than the overall proportion of women (27%), however, since growth is driven by the entry of young women into the field. Also, like most sciences, astronomy has experienced growth over the past few decades, so the aging population is itself relatively small.

Here's something to think about. It took 20 years for the first woman to win the Kuiper. Suppose it takes 15 (2019) before the next woman wins. Then 10 years (2029) for the next. Then five (2034), then three (2037). Then a woman wins every other year (2039, 2041). Hold on! What does it say on Keane's graphs? "Expect parity after 2040." If I'm right, however, we shouldn't expect a woman to win the Kuiper every other year until well after parity has been reached. That is, even if the frequency of female winners increases more slowly than I just suggested, so that a male-female "coin toss" begins to happen only in 2060, that would still be perfectly in line with an assumption of no gender bias in the selection process. [And note that even on my optimistic scenario, by the time the odds that a woman will win in any given year have evened, only 7 out of 57 winners will have been women. That's 12%.]

As far I can tell, then, there is nothing immediately appalling about the Kuiper Prize at the moment. Like telescope time at the ESO, seniority, not gender, is the most important factor. Astronomers know how to sort signal from noise when looking at the stars. I wish they would be as careful with data on themselves.**

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*In a funny twist, Keane, a graduate student, apparently won an award of the same name in 2015. It's not the same one we're talking about here.

**Update: It is worth comparing the Kuiper to the Masursky Prize, which Christina Richey won in 2015 for her work on gender issues. This award is a given "for meritorious service to planetary science" and "is generally given for accomplishments outside of the normal work duties of the nominee." Again, I have only the rough data of a convenience sample. But it looks like it has traditionally been given to people after a long career of service. The average age of the recipients whose ages I could easily determine in the first 20 years of the prize's existence was 67. During that time, two women had won, aged 78 and 67. 16 men won. That's about 11% women. The current 22% is reached because three out of the five most recent winners have been women.

In an interesting detail, two of these have been under forty. One of them is Richey (who I assume is in her mid 30s based on when she did her undergraduate work) and one of them received the award posthumously, having tragically died that year. It should be noted that this appears to be the only year in which she was eligible to be nominated for the award; it can only be given posthumously within a year of the recipient's death. The committee, no doubt rightly, chose to give her the honor she was due while it could. It had only three years to do so after the nomination. I will therefore assume that, had she lived, or had the rule not existed, she would have won the award perhaps two decades later.

Richey's very young age, on this view, is completely unique. The general point here, again, is that it is simply not informative to compare the proportion of women who win these sorts of prizes with the proportion of women in the field. The actual pool of possible winners, because they are generally older, is very likely to be much more male-dominated than the field as a whole, which is approaching parity much more quickly in the younger part of the population. That said, as Richey in fact said in her acceptance speech, her award does seem to have been motivated by a desire to do more than simply honor an individual's past "meritorious service". In 2015, the committee apparently broke with tradition and looked to the future, giving it to someone who was poised to serve a particular agenda.