Is January 2 a rare birthday?

January 2 is one of the least common birthdays in these historical U.S. records. It ranks #361 out of 366 month/day dates, where #1 means most common. Within January it ranks #30 of 31; only January 1 has fewer births.

January 2 had 196,481 recorded births from 1994 through 2014, or 0.229% of the sample. That is about 1 in 436 recorded births, not an estimate of everyone alive who shares the date.

January 1, January 2 and January 3 differ

January 2 has more births than New Year's Day but fewer than January 3. Even these three consecutive dates have quite different recorded totals.

All these dates occurred 21 times in the baseline. January 2 averaged 9,356.2 births per actual occurrence. Its low total comes from fewer recorded births each time it appears, rather than fewer calendar appearances.

The January guide covers the whole month. The January 1 study and December 31 study examine the dates on either side of the year boundary.

When January 2 is the observed New Year's holiday

New Year's Day is January 1, but its federal observed date can move. The Office of Personnel Management explains the usual Monday-through-Friday rule: a Sunday holiday is normally observed on Monday for these federal employees. Within our SSA window, January 1 fell on Sunday in 2006, 2012, making January 2 the observed date.

We compare the actual January 2 birth counts in those years with nearby Mondays. Their signed difference is -30.5%. In the other 13 years, the difference from each year's own same-weekday comparison is -9.1%.

The observed-holiday group contains only 2 dates. The table describes the counts in these small calendar groups. They cannot tell us how much the holiday changed delivery timing. Federal employee holiday rules also do not tell us how every hospital operated.

Does the low count persist across years?

For this separate comparison we use SSA U.S. records from 2000 through 2014. Eligible comparison dates are seven or fourteen days before or after January 2, within the same year and on the same weekday. Actual and standard observed federal holidays, Christmas Eve, December 26 and the Friday after Thanksgiving are removed as controls.

For January 2, the preceding December dates are outside the target year. That leaves January 9 and January 16, except when January 16 is a holiday. Each year's available controls are averaged first; the overall comparison divides the sum of January 2 births by the sum of those annual averages.

Across all 15 years, January 2 is 12.1% below the comparison average. It is lower in 14 years and higher in 1.

Why the fourteen-day check omits two years

Using only seven-day controls gives -12.1% across 15 years. Using only fourteen-day controls gives -9.1% across 13 years, omitting 2006, 2012.

In those omitted years, January 16 was Martin Luther King Jr. Day and the earlier fourteen-day candidate was in the preceding December. Neither is eligible, so those years have no fourteen-day control. OPM's holiday-designation fact sheet places Martin Luther King Jr. Day on the third Monday in January.

Both omitted years are also the observed-New-Year group discussed above. The fourteen-day-only result therefore changes the years being compared as well as the comparison dates. Its smaller gap cannot be read as the same group becoming less unusual under a wider window.

Sources and limits

The baseline uses FiveThirtyEight's daily U.S. birth files: CDC/NCHS for 1994 through 1999 and SSA for 2000 through 2014, excluding overlapping CDC years. The systems differ in administrative coverage. Annual and calendar-group comparisons use SSA alone.

Daily counts do not identify delivery methods, family choices or hospital schedules. Nearby-weekday matching controls one calendar difference and does not establish a cause. See the holiday study for a broader comparison design and the methodology for definitions. Browse the rare-birthday ranking or check your own birthday.