Not especially. March 27 is less common than most dates in these historical U.S. records, but it is not among the rarest. It ranks #270 of 366 dates by total births from 1994 through 2014. Rank #1 means most common.
March 27 had 229,682 births across 21 occurrences, or 10,937 births per occurrence. That is 0.268% of the 85,712,738-birth sample, or about 1 in 373 recorded births.
Within March, March 27 ranks #22 of 31 dates.
Does March 27 differ from nearby same-weekday dates?
It depends on which controls we use. In SSA 2000–2014, the primary comparison gives +0.1%. With only the 7-day controls, the result is -1.0%. With only the 14-day controls, it is +1.4%.
Because the sign changes, these results do not show clearly that March 27 has more or fewer births than nearby dates.
In the primary comparison, March 27 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 March 27 with controls from the same year.
| Comparison | Years | Control observations | Difference |
|---|---|---|---|
| 7 and 14 days, holidays excluded (primary) | 15 | 60 | +0.1% |
| 7 days only | 15 | 30 | -1.0% |
| 14 days only | 15 | 30 | +1.4% |
| 7 and 14 days, no holiday exclusions | 15 | 60 | +0.1% |
How were the comparison dates chosen?
The primary controls are March 13, March 20, April 3, and April 10 in the same year. Each is 7 or 14 days from March 27, 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.
Gregorian Western Easter fell on March 27 once, in 2005. That Sunday had 5.2% fewer births than nearby Sundays. One occurrence cannot show a pattern.
By five-year period, the primary differences are +0.3% for 2000–2004, -0.4% 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 27 rank change over time?
Yes. We ranked 365 recurring dates by SSA births in each five-year period. March 27 placed #149 in 2000–2004, #207 in 2005–2009, and #319 in 2010–2014. The three ranks span 170 places.
The median span for all 365 recurring dates is 159 places. This span is above that median.
Each period has only five occurrences of March 27. It fell on a weekend twice in 2010–2014 and once in each other period. The period with more weekend occurrences has the less common rank.
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.