Superfreakonomics_ global cooling, patri - Steven D. Levitt [27]
Such birth effects aren’t as rare as you might think. Douglas Almond, examining U.S. Census data from 1960 to 1980, found one group of people whose terrible luck persisted over their whole lives. They had more physical ailments and lower lifetime income than people who’d been born just a few months earlier or a few months later. They stood out in the census record like a layer of volcanic ash stands out in the archaeological record, a thin stripe of ominous sediment nestled between two thick bands of normalcy.
What happened?
These people were in utero during the “Spanish flu” pandemic of 1918. It was a grisly plague, killing more than half a million Americans in just a few months—a casualty toll, as Almond notes, greater than all U.S. combat deaths during all the wars fought in the twentieth century.
More than 25 million Americans, meanwhile, contracted the flu but survived. This included one of every three women of childbearing age. The infected women who were pregnant during the pandemic had babies who, like the Ramadan babies, ran the risk of carrying lifelong scars from being in their mothers’ bellies at the wrong time.
Other birth effects, while not nearly as dire, can exert a significant pull on one’s future. It is common practice, especially among economists, to co-write academic papers and list the authors alphabetically by last name. What does this mean for an economist who happened to be born Albert Zyzmor instead of, say, Albert Aab? Two (real) economists addressed this question and found that, all else being equal, Dr. Aab would be more likely to gain tenure at a top university, become a fellow in the Econometric Society (hooray!), and even win the Nobel Prize.
“Indeed,” the two economists concluded, “one of us is currently contemplating dropping the first letter of her surname.” The offending name: Yariv.
Or consider this: if you visit the locker room of a world-class soccer team early in the calendar year, you are more likely to interrupt a birthday celebration than if you arrive later in the year. A recent tally of the British national youth leagues, for instance, shows that fully half of the players were born between January and March, with the other half spread out over the nine remaining months. On a similar German team, 52 elite players were born between January and March, with just 4 players born between October and December.
Why such a severe birthdate bulge?
Most elite athletes begin playing their sports when they are quite young. Since youth sports are organized by age, the leagues naturally impose a cutoff birthdate. The youth soccer leagues in Europe, like many such leagues, use December 31 as the cutoff date.
Imagine now that you coach in a league for seven-year-old boys and are assessing two players. The first one (his name is Jan) was born on January 1, while the second one (his name is Tomas) was born 364 days later, on December 31. So even though they are both technically seven-year-olds, Jan is a year older than Tomas—which, at this tender age, confers substantial advantages. Jan is likely to be bigger, faster, and more mature than Tomas.
So while you may be seeing maturity rather than raw ability, it doesn’t much matter if your goal is to pick the best players for your team. It probably isn’t in a coach’s interest to play the scrawny younger kid who, if he only had another year of development, might be a star.
And thus the cycle begins. Year after year, the bigger boys like Jan are selected, encouraged, and given feedback and playing time, while boys like Tomas eventually fall away. This “relative-age effect,” as it has come