Weekdays average more births per day
Weekdays averaged 12,674.6 births per day, compared with 8,040.5 on weekends, in the U.S. SSA records from 2000 through 2014. An average weekend day had 36.6% fewer births than an average weekday.
Simply counting all weekday births would give weekdays an advantage: there are five weekdays and only two weekend days in a normal week. Dividing by the number of actual days lets us compare their daily averages.
| Group | Recorded births | Observed days | Births per day |
|---|---|---|---|
| Monday to Friday | 49,595,640 | 3,913 | 12,674.6 |
| Saturday and Sunday | 12,591,384 | 1,566 | 8,040.5 |
What is the most common day of the week to be born?
Tuesday has the highest average, at 13,122.4 recorded births per Tuesday. Sunday has the lowest, at 7,518.4 per Sunday. Every weekday has a higher average than either Saturday or Sunday in this dataset.
| Day | Recorded births | Observed days | Births per day |
|---|---|---|---|
| Monday | 9,316,001 | 783 | 11,897.8 |
| Tuesday | 10,274,874 | 783 | 13,122.4 |
| Wednesday | 10,109,130 | 783 | 12,910.8 |
| Thursday | 10,045,436 | 782 | 12,845.8 |
| Friday | 9,850,199 | 782 | 12,596.2 |
| Saturday | 6,704,495 | 783 | 8,562.6 |
| Sunday | 5,886,889 | 783 | 7,518.4 |
The period contains 783 occurrences of most days of the week, but 782 Thursdays and Fridays. Each average uses the actual number of times that day occurred.
Weekdays also have the higher daily average in each of the 15 individual years. The difference appears throughout the period.
Why are fewer babies born on weekends?
The file contains dates and birth counts. It has no information about labor onset, delivery method, or why a delivery happened on a particular day, so it cannot explain the weekend difference by itself.
A separate NCHS table for U.S. births in 2014, Table I-3, breaks out weekday patterns by vaginal and cesarean delivery. It also shows lower weekend averages, with a larger weekend reduction in the cesarean category relative to that category's daily average. Those are birth-certificate records for 2014, separate from our SSA analysis covering 2000 through 2014.
The NCHS table shows how the weekday pattern differs by delivery type. It does not establish why any individual delivery occurred when it did, and our aggregate comparison cannot separate scheduled deliveries from other births.
How we counted weekdays and weekends
We used all 62,187,024 births across 5,479 dates in the SSA file, from January 1, 2000 through December 31, 2014. Monday through Friday count as weekdays; Saturday and Sunday count as weekends. Holidays retain their actual weekday classification.
Average births per day = births in the group ÷ actual days in the group
For weekdays, that is 49,595,640 ÷ 3,913. For weekends, it is 12,591,384 ÷ 1,566. To calculate how much lower the weekend average is, we subtract the weekend-to-weekday average ratio from one and multiply by 100.
We use one source series throughout. The main birthday checker combines CDC/NCHS 1994 through 1999 with SSA 2000 through 2014, so its coverage and totals are different. These daily averages adjust for the number of days in each group; they do not adjust for the mix of holidays or other factors affecting birth counts.
Sources and related comparisons
The calculations use FiveThirtyEight's SSA daily birth file, shared under CC BY 4.0 as described in the repository. Download the analysis data for the numerical results. See the methodology for the source and calculation boundaries.
The findings describe historical U.S. records. They are not a prediction of an individual baby's birth date or a claim about today's worldwide pattern.
You can also compare birth months: August leads by total births, while September leads per day. For a closer look at particular calendar dates, see births around four selected holidays or use the birthday checker.