Is July 29 a rare birthday?

July 29 ranks #75 of 366 dates in historical U.S. birth records, 1994–2014. It is slightly below nearby same-weekday dates, but the evidence is weak.

Reviewed

No. July 29 has more recorded births than most dates in these historical U.S. records. It ranks #75 of 366 dates by total births from 1994 through 2014. Rank #1 means most common.

July 29 had 244,166 births across 21 occurrences, or 11,627 births per occurrence. That is 0.285% of the 85,712,738-birth sample, or about 1 in 351 recorded births.

It ranks #20 of the 31 July dates.

Does July 29 differ from nearby same-weekday dates?

July 29 has slightly fewer births than its controls in every planned comparison. In SSA 2000–2014, the primary comparison gives -1.0%. The planned comparisons range from -0.6% to -1.5%.

The 7-day comparison differs by less than 1%, so we treat the result as weak.

In the primary comparison, July 29 was above its controls in four years and below them in eleven.

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 July 29 with controls from the same year.

July 29 births compared with same-weekday controls, SSA 2000–2014.
ComparisonYearsControl observationsDifference
7 and 14 days, holidays excluded (primary)1560-1.0%
7 days only1530-0.6%
14 days only1530-1.5%
7 and 14 days, no holiday exclusions1560-1.0%

How were the comparison dates chosen?

The primary controls are July 15, July 22, August 5, and August 12 in the same year. Each is 7 or 14 days from July 29, 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, -0.4% for 2005–2009, and -1.8% 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 July 29 rank change over time?

Yes. We ranked 365 recurring dates by SSA births in each five-year period. July 29 placed #207 in 2000–2004, #211 in 2005–2009, and #55 in 2010–2014. The three ranks span 156 places.

The median span for all 365 recurring dates is 159 places. This span is close to that median.

Each period has only five occurrences of July 29. 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 July guide for the full month ranking. See also the July 1 and July 4 studies.

The methodology explains ranks and shares. Use the birthday checker to compare another date.