Not especially. March 11 is less common than most dates in these historical U.S. records, but it is not among the rarest. It ranks #251 of 366 dates by total births from 1994 through 2014. Rank #1 means most common.
March 11 had 230,308 births across 21 occurrences, or 10,967 births per occurrence. That is 0.269% of the 85,712,738-birth sample, or about 1 in 372 recorded births.
Within March, March 11 ranks #18 of 31 dates.
Does March 11 differ from nearby same-weekday dates?
Not clearly. In SSA 2000–2014, the primary comparison gives -0.5%. The three comparisons with holiday exclusions all stay within 1% of the controls.
When weekdays match, March 11 looks much like the dates around it.
In the primary comparison, March 11 was above its controls in five years and below them in ten.
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 March 11 with controls from the same year.
| Comparison | Years | Control observations | Difference |
|---|---|---|---|
| 7 and 14 days, holidays excluded (primary) | 15 | 60 | -0.5% |
| 7 days only | 15 | 30 | -0.6% |
| 14 days only | 15 | 30 | -0.5% |
| 7 and 14 days, no holiday exclusions | 15 | 60 | -0.5% |
How were the comparison dates chosen?
The primary controls are February 25, March 4, March 18, and March 25 in the same year. In leap years, the February control is February 26. Each is 7 or 14 days from March 11, so it falls on the same weekday.
None of these controls fell on an excluded holiday. We exclude holidays under the standard observed federal holiday rules. We also exclude Christmas Eve, December 26, and the Friday after Thanksgiving.
By five-year period, the primary differences are -0.9% for 2000–2004, -0.1% for 2005–2009, and -0.6% 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 March 11 rank change over time?
Somewhat, but less than most dates. We ranked 365 recurring dates by SSA births in each five-year period. March 11 placed #307 in 2000–2004, #299 in 2005–2009, and #207 in 2010–2014. The three ranks span 100 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 March 11. It fell on a weekend twice in 2000–2004, twice in 2005–2009, and once in 2010–2014. 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 March guide for the full month ranking. Compare the nearby March 17 study.
The methodology explains ranks and shares. Use the birthday checker to compare another date.