For millennia, people have used birth dates to divine details about an individuals personality, abilities, and even intelligence. Astrology is certainly one of the longest running practices, but scientific research in the past few decades has brought the idea of birthday-linked traits into the mainstream. One study published in 1991 was considered particularly groundbreaking: It claimed that people born in winter months achieve lower levels of education. From there, the floodgates opened, and those born on one of the year’s shorter days were soon doomed to die earlier after enduring lower pay and poorer health.
But the explanation for those myriad (and depressing) results may all boil down to a simple matter of socioeconomics according to a recent working paper brought to my attention by Paola Sapienza, professor of finance. She also pointed me to a thorough summary of the research published in the Wall Street Journal. The two scientists behind the research, Notre Dame economists Kasey Buckles and Daniel Hungerman, were talking to each other about their individual projects one day when they notice a trend that cut across both their studies. Less educated women appeared to give birth more often in winter.
“Honestly, when we first saw these patterns, we were so stunned we wondered if we made some mistake,” Hungerman said in the WSJ article.
The trend was no mistake, though. While small, it was statistically significant and cut across a few other socioeconomic markers. In addition to lower educational achievement, mothers of winter babies are more often single and more likely to be teenagers.
Experts don’t have a sound explanation for the phenomenon at this point. Hypotheses range from the influence of hot summer temperatures on lower conception rates (the poor are less likely to have air conditioning, decreasing summer conceptions) to the “prom” effect (“January is, after all, about nine months after many of those soirees,” notes the WSJ article).
What the article has done, though, is call into question the importance and even validity of previous findings in the field. The winter-achievement-gap phenomenon has been used most prominently to prove the impact of education on earnings later in life. While few doubt the value of a good education, proving it scientifically may be more difficult than we thought.