October 31 is the rarest October birthday in these historical U.S. records. It ranks #356 of 366 dates, where #1 means most common. Its 210,629 recorded births account for 0.246% of the 1994 through 2014 total, or about 1 in 407 recorded births.
A separate comparison using only SSA records from 2000 through 2014 finds fewer births on Halloween than on nearby dates of the same weekday in every year studied. The October birthday guide covers all dates in the month; the annual table below follows Halloween itself.
October 31, beside other birthdays
Average recorded births each time a date occurred, 1994 through 2014.
- Commonness rank
- 356 / 366
- Share of recorded births
- 0.246 %
- Recorded births
- 210,629
Bars start at zero. Rank 1 means most common and uses total births across all 366 dates. The bars use births per actual occurrence; February 29 appeared five times, while the other dates appeared 21 times.
Check October 31 and compare with a friend →How does October 31 compare with nearby birthdays?
The difference is visible either side of Halloween. October 30 and November 1 both have higher recorded totals in the 1994 through 2014 baseline. October 1, the busiest October birthday, is included for a broader month comparison.
| Date | Recorded births | Commonness rank | Birth share |
|---|---|---|---|
| October 1 | 247,196 | 47 | 0.288% |
| October 24 | 237,881 | 127 | 0.278% |
| October 30 | 228,305 | 299 | 0.266% |
| October 31 | 210,629 | 356 | 0.246% |
| November 1 | 239,419 | 110 | 0.279% |
All these dates occurred once a year across the same period. Halloween's low total does not come from fewer calendar appearances, as February 29's does. October 31 averaged 10,030 births across its 21 appearances in this baseline.
Adjacent dates still fall on different weekdays. Since weekend and weekday birth counts differ, a comparison with October 30 alone cannot show whether Halloween is unusual for its weekday.
Is the Halloween gap consistent across years?
For each Halloween from 2000 through 2014, we averaged the birth counts on October 17, October 24, November 7, and November 14 of the same year. These dates sit one or two weeks either side of Halloween, so all five dates share a weekday.
Halloween averaged 10,262.8 recorded births, against 11,714.7 on the nearby dates: 12.4% fewer. It was below the nearby average in all 15 SSA years, although the size of the gap varied. A negative percentage in the table means fewer births on Halloween than on its comparison dates.
| Year | Weekday | Recorded births | Nearby mean | Difference |
|---|---|---|---|---|
| 2000 | Tuesday | 11,372 | 13,019 | -12.7% |
| 2001 | Wednesday | 10,913 | 12,574 | -13.2% |
| 2002 | Thursday | 10,850 | 12,581 | -13.8% |
| 2003 | Friday | 11,005 | 12,552.5 | -12.3% |
| 2004 | Sunday | 7,556 | 7,649.3 | -1.2% |
| 2005 | Monday | 10,207 | 12,145.5 | -16.0% |
| 2006 | Tuesday | 12,064 | 14,116.3 | -14.5% |
| 2007 | Wednesday | 11,757 | 13,827.3 | -15.0% |
| 2008 | Friday | 11,013 | 12,964 | -15.0% |
| 2009 | Saturday | 7,658 | 8,208.3 | -6.7% |
| 2010 | Sunday | 6,895 | 7,198.5 | -4.2% |
| 2011 | Monday | 9,828 | 11,685 | -15.9% |
| 2012 | Wednesday | 11,012 | 12,656.5 | -13.0% |
| 2013 | Thursday | 10,975 | 12,328 | -11.0% |
| 2014 | Friday | 10,837 | 12,215.5 | -11.3% |
The gap was smaller when Halloween fell on a weekend. That matters when reading a single year's raw count: a quiet Sunday is a different comparison from a busy Tuesday. Matching weekdays keeps that difference from being the whole explanation, although it cannot remove every seasonal change around the date.
Why might fewer babies be born on Halloween?
These SSA records give daily totals. They do not identify delivery methods, hospital schedules, or a family's reasons for choosing a date.
A separate study of U.S. birth certificates from 1996 through 2006 found lower spontaneous and cesarean birth counts on Halloween after accounting for weekday and year. The Yale researchers' report discusses cultural beliefs as a possible influence on birth timing.
That study uses different data and a different comparison. It provides context for the pattern; it does not establish why any birth in our table happened on October 31 or another day. The annual gaps also do not count births that were prevented or moved elsewhere.
What does the birthday probability mean?
The share describes births recorded in the historical dataset. It is not the probability of a particular pregnancy ending on Halloween, a current birth forecast, or a count of living people who share your date. The full rare-birthday ranking compares Halloween with the rest of the calendar, and the birthday checker lets you compare any two dates.
Our baseline comes from daily U.S. birth records compiled by FiveThirtyEight: CDC/NCHS for 1994 through 1999, followed by SSA for 2000 through 2014 without overlapping years. The annual table uses SSA alone. The methodology explains the different source coverage and how ranks and shares are calculated.
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