The image above shows "each day of the year with a ranking for how many babies were born in the United States on each date from 1973 to 1999." Obviously, more people were born in Jul/Aug/Sep than in Jan/Feb/Mar. But after the chart was published in The Daily Viz, the creator found it necessary to publish a clarification -
While I’m excited about the traffic, I’m also worried that the graphic may have misled some readers. Some people read the map assuming that darker shades represented higher numbers of actual births, even though I tried to explain in the post that the colors were shaded by birthday rank, from 1 to 366, in popularity. Or I thought I did. Because of that, Sept. 16 — the most popular birthday — seems wildly more common than January 1, among the least popular. Both may be relatively close in the raw number of births, even though their ranks are far apart.Here's a followup graph showing births/month (and normalized for number of days in the month):
What I actually find most interesting about the first heat map is the extent to which modern medical technology allows birth days to be manipulated - the obvious gaps at the Fourth of July and the days closest to Christmas, with the darker shades just before and after those holidays.
I like the pale row running right across the image on the 13th.
ReplyDeleteThat's interesting too. I wonder if he could break down his data by which 13ths were on Fridays?
DeleteOr a Fourth of July that falls on a Friday the 13th.
Delete"Some people read the map assuming that darker shades represented higher numbers of actual births, even though I tried to explain in the post that the colors were shaded by birthday rank, from 1 to 366, in popularity."
ReplyDeleteI'm confused. How doesn't actual births = popularity? Are people choosing their birthdays now? Or was this chart mapping how people feel about different birth dates?
I agree that his explanation is infelicitous; presumably he's better with numbers than with words. What I think he meant to say is that the DEGREE of darkness does not correlate with the number of births (i.e. something twice as dark is not twice as many births, and something pale does not imply a near-absence).
DeleteSo then what information is actually being delivered??? Something that seems obvious is actually confusing.
DeleteThe most common birthdates look to be roughly 9 months after Valentines Day. Just saying.
ReplyDeleteThey look to me to be about 8.5 months (40 weeks, more or less) after New Year's Day.
DeleteLook also at the blip-up on 14th Feb Valentine's Day itself and a similar excess on Patrick's Day. My Grandmother was born on Feb 14 1892 and called Lily Valentine, so it looks like loyal Irish Americans are scheduling their C-sections for Paddy's Day, so that they won't forget when Patrick Jr's birthday is.
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