data

US births by day data is available here: https://github.com/fivethirtyeight/data/tree/master/births For the period 2000-2014 the number of births by month, divided by the number of days in a month, is: 1 31 5 072 588 163 631.87 2 28 4 725 693 168 774.75 3 31 5 172 961 166 869.71 4 30 4 960 750 165 358.33 5 31 5 195 445 167 595.00 6 30 5 163 360 172 112.00 7 31 5 450 418 175 819.94 8 31 5 540 170 178 715.16 9 30 5 399 592 179 986.40 10 31 5 302 865 171 060.16 11 30 5 008 750 166 958.33 12 31 5 194 432 167 562.32 365 62 187 024 170 375.41 The difference isn't huge but it's significant. There were on average 180k birth in Sept. vs 165k in April and 170k in December. Edit: also,

If we're going off of rarity, December 25 has 6,574 average yearly births and September 9 has almost double at 12,301 average yearly births. Taking a look at Feb 29th, it has 10467 average yearly births (for years that have a Feb 29th). So what is the level of rarity that makes a day not worth calculating? https://github.com/fivethirtyeight/data/blob/master/births/U...