Birthday Rankings Explained
Understand how recorded U.S. birth counts from 2000–2014 become birthday rankings. The statistics use recorded U.S. births from 2000–2014; birthday symbols and traditions are presented separately.
Ranking Terms
- U.S. rank (2000–2014)
- A comparison of total recorded U.S. births for each of the 366 month-and-day combinations in 2000–2014.
- Commonness
- A browsing label based on a date’s rank in the U.S. 2000–2014 birth counts.
- Rarity
- A practical way to talk about dates that appear less often or feel more unusual because of calendar timing.
Why Rankings Differ
The current rankings describe recorded U.S. births from 2000–2014. They can differ from other lists because of the country, period and treatment of leap day. The method below explains exactly which counts we use.
For a fast comparison, try How Rare Is My Birthday?.
The Data Behind the Rankings
We use the file US_births_2000-2014_SSA.csv, published by FiveThirtyEight and identified in its documentation as U.S. birth data provided by the Social Security Administration. It contains 5,479 daily rows from January 1, 2000 through December 31, 2014, totaling 62,187,024 births.
How We Calculate Rank and Share
We add the birth counts for each month-and-day combination across all fifteen years, then sort these 366 totals from largest to smallest. Rank #1 is the largest total. Equal totals share a rank, with the following rank skipped. The percentage is that date’s total divided by 62,187,024, multiplied by 100. Displayed percentages are rounded.
February 29: Total Births vs. Births per Occurrence
February 29 occurred in 2000, 2004, 2008 and 2012. Its 41,869 recorded births are included in the total-birth ranking, where it is #366. Dividing by four gives 10,467.3 births per occurrence. Other dates have fifteen occurrences. Ranking by per-occurrence averages would answer a different question and would change leap day’s position.
What These Numbers Can Tell You
The results describe this historical U.S. dataset. They do not measure birthdays worldwide, the birthday distribution of everyone alive today, or the probability of a future baby arriving on a particular day. Different countries, periods and counting methods can produce different ranks. Annual counts also reflect changes in total births and the weekdays on which a date falls.
The labels “more common” (ranks 1–60), “middle of the calendar” (61–309) and “rarer” (310–366) are browsing labels chosen by this site, not statistical significance tests. Earlier versions used a seasonal estimate; the current rankings are calculated from the recorded birth counts.
Date Calculator Conventions
Countdowns use your device’s local calendar date. A birthday today returns zero days. For a February 29 birthday, the annual countdown uses February 28 in a non-leap year; the leap-day result separately shows the next actual February 29. Age calculations count completed years, then completed months, then remaining days. A month-end anniversary is clamped to the last day of a shorter month. Future birth dates are rejected. These are calendar conventions, not rules for legal age.
Source: U.S. births, 2000–2014, from the Social Security Administration dataset published by FiveThirtyEight. BirthdayStatistics.com aggregates the recorded counts by month and day. Data licensed CC BY 4.0. Method and limitations.