These Are the Most Common Birthdays—And the Least

Turns out, the holidays are a very popular time to conceive, but not to give birth, according to real birth data.

Knowing your due date means knowing much more than when you can expect your little one to arrive. It will determine anything and everything from the logistics around your labor and delivery to the time of year your child will celebrate their birthday.

Curious to know if your kid on the way will be celebrating during the most common birthday month along with plenty of classmates? Or maybe they'll be born on the least common day of the year for babies to make their big entrance into the world? Thanks to a viral blog post from The Daily Viz's Matt Stiles, you can figure that out.

The Data

Arguably the coolest part of Stile's viral post is that the data is spread out in a colorful heat map, making the numbers less of a headache to sift through. The beautiful display reveals that September is a busy month for birthing.

But the data also shows that as much fun as it is to figure out how rare your birthday may (or may not) be, the system has a teeny flaw: The busiest days for births are not that much busier than the rarer days. As the author notes, the busiest days on the calendar have 12,000 births, and the least busy have around 6,500 with 11,00 as the median.

Still, it is pretty fun to check out. Curious to see where your child's expected birthday lands? Here's the scoop on the most common birthdays in the U.S.

The Most Common Birth Month

Using real birth data (covering 20 years of American births) gathered by FiveThirtyEight from the National Center for Health Statistics and Social Security Administration, Stiles concluded that September is the most popular month to give birth to a child in the U.S. In fact, nine of the top 10 days to give birth fall between September 9 and September 20.

So, then, the question is, of course, why?

"If you back up 38 weeks, that means many couples are conceiving in December and around the holidays," explains Whitney Casares, M.D., M.P.H., F.A.A.P., author of The New Baby Blueprint: Caring for You and Your Little One. "It makes sense that they may be more likely to conceive during more celebratory seasons."

Another reason, Dr. Casares points out: According to a study in Obstetrics and Gynecology, couples may have more luck conceiving during the winter season due to higher-quality sperm in winter versus summer months. "They also postulated that changes in daylight length might make an ovum’s environment better-suited for a sperm," she notes. "More research is needed to understand this interesting phenomenon.

The Most Common Birthdays

Experian landed on September 9 as the most common birthday in the U.S. It's shared by comedian Adam Sandler, actor Hugh Grant, jazz singer Michael Bublé, Russian literary giant Leo Tolstoy, and Colonel Sanders, the founder of KFC. September 19 is the second most common birthday, followed by September 12, September 17, September 10, and the first non-September date in the mix: July 7.

Top 10 Most Common Birthdays
Rank Date U.S. Average Daily Births
1st September 9 (9/9) 12,301
2nd September 19 (9/19) 12,229
3rd September 12 (9/12) 12,224
4th September 17 (9/13) 12,148
5th  September 10 (9/10) 12,143
6th July 7 (7/7) 12,108
7th September 20 (9/20) 12,107
8th September 15 (9/15) 12,087
9th September 16 (9/16) 12,072
10th September 18 (9/18) 12,055
Data: U.S. National Center for Health Statistics (1994-2003) and U.S. Social Security Administration (2004-2014) via FiveThirthyEight Credit: Matt Stiles/The Daily Viz

The Least Common Birthdays

The least common birthdays in the U.S. interestingly all hover around major holidays. December 25 (Christmas Day) is the least common birthday, while January 1 (New Year's Day) is the second least common. December 24 (Christmas Eve) also makes the list as the 3rd least common birthday while July 4 (Independence Day) is the 4th least common birthday.

Several of the least common birthdays also hover around Thanksgiving (the fourth Thursday in November), which can fall anywhere between November 22 and November 28. The 10th least common birthday is October 31 (Halloween).

Top 10 Least Common Birthdays
Rank Date U.S. Average Daily Births
366th December 25 (12/25) 6,574
365th January 1 (1/1) 7,792
364th December 24 (12/24) 8,069
363rd July 4 (7/4) 8,796
362nd January 2 (1/2) 9,307
361st December 26 (12/26) 9,543
360th November 27 (11/27) 9,718
359th November 23 (11/23) 9,883
358th November 25 (11/25) 9,954
357th October 31 (10/31) 9,978
Data: U.S. National Center for Health Statistics (1994-2003) and U.S. Social Security Administration (2004-2014) via FiveThirthyEight Credit: Matt Stiles/The Daily Viz

The Bottom Line

So if you happen to be expecting around the holidays, your child likely won't have all that much competition for celebration growing up. But if you happened to conceive during the holidays, get ready for an avalanche of cupcakes and many performances of the "Birthday Song" come September.

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