Not especially. November 30 is less common than most dates in these historical U.S. records, but it is not among the rarest. It ranks #289 of 366 dates by total births from 1994 through 2014. Rank #1 means most common.
November 30 had 228,854 births across 21 occurrences, or 10,898 births per occurrence. That is 0.267% of the 85,712,738-birth sample, or about 1 in 375 recorded births.
Within November, November 30 ranks #21 of 30 dates.
Seven of its 21 occurrences fell on a Saturday or Sunday. The average across all dates is 6.0. Weekend days have fewer recorded births, so this calendar mix can lower its total. This comes from the calendar in these years, not from the date itself.
Does November 30 differ from nearby same-weekday dates?
It depends on which controls we use. In SSA 2000–2014, the primary comparison gives -0.8%. With only the 7-day controls, the result is +0.4%. With only the 14-day controls, it is -1.4%.
Because the sign changes, these results do not show clearly that November 30 has more or fewer births than nearby dates.
In the primary comparison, November 30 was above its controls in six years and below them in nine.
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 November 30 with controls from the same year.
| Comparison | Years | Control observations | Difference |
|---|---|---|---|
| 7 and 14 days, holidays excluded (primary) | 15 | 55 | -0.8% |
| 7 days only | 15 | 25 | +0.4% |
| 14 days only | 15 | 30 | -1.4% |
| 7 and 14 days, no holiday exclusions | 15 | 60 | +2.4% |
How were the comparison dates chosen?
The primary controls are November 16, November 23, December 7, and December 14 in the same year. Each is 7 or 14 days from November 30, 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 -0.8% to +2.4%. Holiday controls usually have fewer births in these records, so including them makes November 30 look higher.
By five-year period, the primary differences are -0.8% for 2000–2004, -1.0% for 2005–2009, and -0.4% 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 November 30 rank change over time?
Somewhat, but less than most dates. We ranked 365 recurring dates by SSA births in each five-year period. November 30 placed #280 in 2000–2004, #168 in 2005–2009, and #272 in 2010–2014. The three ranks span 112 places.
The median span for all 365 recurring dates is 159 places. This span is below that median.
Each period has only five occurrences of November 30. 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 November guide for the full month ranking. Compare the nearby November 29 and November 27 studies.
The methodology explains ranks and shares. Use the birthday checker to compare another date.