October 5th is the most common birthday! Check the internet1 and most sites say it's the truth. However a New York Times survey2 reported that day to be September 16th. Then again the 2010 census reported it to be October 10th3. However all these surveys report August through October as the most common birth month, so that any of these dates could be the most popular birthday. The explanation is that conception probably takes place shortly before the New Year begins -- with an idea of renewal in the form of a child.

Historically, however, this has not been true. Dan Rogers of Albany, Oregon has analyzed birthdays of the last 400 years at his genealogy website. He shows that the most popular birthday has been January 1st -- followed by February 14th. New Year's Day has been 65% more popular than the average day. Why do you think this is true? Do you think a mother can choose these special birthdays for her child? Rogers maintains that within a day or two a mother can change the date. As evidence he notes that the days before and after New Year's Day and Valentine's Day have been significantly less common as birthdates.

The other internet sites also note that Christmas Day currently is very unpopular as a birthday. Perhaps this is because people want their children to have a birthday different from Jesus. However in bygone days Christmas births were much more popular with significantly fewer birthdates on the 24th and 26th.

There has been no strong bias showing July 4th to be a particularly popular birthdate. Before and after 1776, Independence Day per capita births have been nearly the same.

Halloween has been an unpopular date in bygone times -- but not these days. Nowadays with all the trick-or-treaters at our doorsteps we don't consider Halloween birthdays as bad omens.

Furthermore Rogers notes that the most common birth month in past years has been March -- not August through October. Why is this so? Rogers has found a correlation between marriage dates and children's birthdays. Marriages formerly were in November and December while present-day ones are in June. This shows that the most popular time to conceive babies is 6 months after their marriage anniversary. Certainly not everyone does this, but there is an internal bias pushing us to do it that way.

Were you married in June? Then your babies will likely be conceived in December and born in September. In times gone by, they married in December, conceived in June, gave birth in March.

1. http://funky-facts.blogspot.com/2009/01/most-common-birthday-day.html

2. http://www.nytimes.com/2006/12/19/business/20leonhardt-table.html?_r=1&ex=1167800400&en=5eb722515916264d&ei=5070

3. http://www.dumblittledoctor.com/analytics_tutorial_most_often_birthday_date.html


The four centuries summarized do not add up to the total -- because pre-1600 data is also included.

Birthday Total Aft. 1900 1800's 1700's 1600's
Dec. 30107143336 23
Dec. 319817323611
Jan. 120623516651
Jan. 212113323734
Jan. 312016293933
. . .
Feb. 1213717365226
Feb. 1314023343840
Feb. 1419624525953
Feb. 1513214383640
Feb. 1614117284444
. . .
Oct. 29 97 14 15 42 23
Oct. 30 153 16 37 60 36
Oct. 31 91 23 22 28 13
Nov. 1 150 17 36 39 45
Nov. 2 130 17 36 45 25
. . .
Dec. 23 114 9 36 37 30
Dec. 24 109 15 31 35 24
Dec. 25 142 16 41 47 29
Dec. 26 95 10 23 37 23
Dec. 27 128 14 36 51 21


MonthAllAft. 19001800's1700's1600's
January 402751710111339975
February 408148599813861049
April 405453010171461862
July 35845729501216698
August 386856410001313816
October 401254010001432876
November 37565199611261841
December 368948410051268803
Total 47,067643812,08215,99110,483


MonthAll1600's1700's1800'sAft. 1900
Jan.4183685 17051093403
Feb.3402509 1316853415
Mar.3488568 1330871379
Apr.3355578 1227884465
May3635701 1319764543
Jun.3594524 1113720959
Jul.2824426 942618553
Aug.2764352 935597646
Sep.3296461 1009916663
Oct.3954641 13781073575
Dec.4648936 18611159563
Total43,9797330 15,99210,7286728
Avg.3665611 1333894561

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