Thirteen years ago, Doug Drinen first looked at NFL player birth days (the month and the day, not the year) at the old PFR Blog. Six years ago, I took a second look at that study. And over the last two days, I spent time looking not just at when NFL players were born, but when people are born in the United States. Today is a continuation of those studies.
There have been 17,027 players to enter the NFL and play in a game since 1970. Given what we know about the birth rate in the United States, we can then estimate how many NFL players should have which birth date. For example, the most common birthday, according to one study, is September 9th. Roughly 0.303% of all U.S. babies are born on this day, which means we would “expect” there to be 51.5 players in this time period with 9/9 birthdays. It turns out that there have been 48, which is pretty close. September 8th is the date with the most NFL players since 1970 — 72 — compared to an expected result of 50.2 players.
Those are just two dates, of course, so let’s look at the entire calendar. I performed this same calculation for every date. As it turns out, January 1st is the biggest outlier: it is a very rare day for babies to be born, but it’s actually an above-average day for NFL players. More on that in a minute. To smooth out the chart, I looked at 31-day periods, so the month of July would be captured by looking at July 16th on the draft (each data point represents that day, along with the 15 days before and after).
Two other notes. For the ends of the year — early January and late December — I pro-rated the numbers to make them work while still using just calendar year cut-offs. [1]Specifically, here’s what I did. For days before January 7th, I excluded due to small sample size. Beginning on January 7th, I looked at the 7 days from the 1st to the 7th, and then … Continue reading The blue line represents the actual number of NFL players born in each 31-day window. The orange line? That represents the estimated number of NFL players based on the birth rates for the United States. [continue reading…]
References
| ↑1 | Specifically, here’s what I did. For days before January 7th, I excluded due to small sample size. Beginning on January 7th, I looked at the 7 days from the 1st to the 7th, and then multiplied that result by 31 divided by 7. For January 8th, I looked at the players born from the 1st to the 8th, and multiplied that result by 31 and divided by 8. And so on, until I got to January 16th. I used the same methodology for the end of December. |
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