No. December 1 has more recorded births than most dates in these historical U.S. records. It ranks #137 of 366 dates by total births from 1994 through 2014. Rank #1 means most common.
December 1 had 237,160 births across 21 occurrences, or 11,293 births per occurrence. That is 0.277% of the 85,712,738-birth sample, or about 1 in 361 recorded births.
It ranks #13 of the 31 December dates.
Does December 1 differ from nearby same-weekday dates?
December 1 has slightly more births than its controls in every planned comparison. In SSA 2000–2014, the primary comparison gives +1.6%. The planned comparisons range from +0.9% to +4.4%.
The 14-day comparison differs by less than 1%, so we treat the result as weak.
In the primary comparison, December 1 was above its controls in nine years and below them in six.
Baseline ranks use historical U.S. CDC/NCHS and SSA records, 1994–2014. The percentage differences use SSA 2000–2014 alone. Each table row compares December 1 with controls from the same year.
| Comparison | Years | Control observations | Difference |
|---|---|---|---|
| 7 and 14 days, holidays excluded (primary) | 15 | 56 | +1.6% |
| 7 days only | 15 | 26 | +2.6% |
| 14 days only | 15 | 30 | +0.9% |
| 7 and 14 days, no holiday exclusions | 15 | 60 | +4.4% |
How were the comparison dates chosen?
The primary controls are November 17, November 24, December 8, and December 15 in the same year. Each is 7 or 14 days from December 1, so it falls on the same weekday.
In some years, a planned control falls on Thanksgiving Day or the Friday after it. We remove a Thanksgiving control under the standard observed federal holiday rules. The Friday after Thanksgiving is not a federal holiday, but this study also excludes it. The year keeps its other controls.
Without holiday exclusions, the result changes from +1.6% to +4.4%. Holiday controls usually have fewer births in these records, so including them makes December 1 look higher.
By five-year period, the primary differences are -0.2% for 2000–2004, +1.5% for 2005–2009, and +3.5% for 2010–2014.
To combine the years, we divide the summed target births by the summed annual control means. Then we subtract one and multiply by 100. The result is not an average of annual percentages.
Does the December 1 rank change over time?
Yes, more than most dates. We ranked 365 recurring dates by SSA births in each five-year period. December 1 placed #295 in 2000–2004, #60 in 2005–2009, and #230 in 2010–2014. The three ranks span 235 places.
The median span for all 365 recurring dates is 159 places. This span is well above that median.
Each period has only five occurrences of December 1. It fell on a weekend twice in 2000–2004, twice in 2010–2014, and once in 2005–2009. The periods with more weekend occurrences have less common ranks.
These ranks use raw birth counts. The ranking-stability study also compares annual shares and weekday-relative scores for every date.
Sources and limits
Baseline totals and ranks use FiveThirtyEight’s pinned U.S. birth files. We use CDC/NCHS for 1994–1999 and SSA for 2000–2014, so no year comes from both sources. Annual comparisons use SSA alone.
The source series have different administrative coverage. These records do not describe worldwide births, everyone alive today, or current birth rates.
The daily totals do not record delivery methods or scheduling decisions. Weekday matching does not remove every seasonal difference. Federal holiday rules identify calendar dates, not hospital schedules.
Use the December guide for the full month ranking. See also the December 24 and December 25 studies.
The methodology explains ranks and shares. Use the birthday checker to compare another date.