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Halloween/Valentine’s update

A few months ago we reported on a claim that more babies are born on Valentine’s Day and fewer on Halloween.

At the time, I wrote that I’d like to see a graph with all 366 days of the year. It would be easy enough to make. That way we could put the Valentine‚Äôs and Halloween data in the context of other possible patterns.

Joshua Gans sent along the following from an unpublished appendix to his paper. It’s not the graph I was asking for but it does supply additional information beyond those two holidays. Click to enlarge:

I don’t know what all those digits are doing (do you really need to know that an estimate is “-70.856” if its standard error is “10.640”? I’d think that “-71 +/- 10 would be just fine), but I suppose the careful reader can ignore the numbers and simply read the signs and the stars. In any case, it’s good to see more data.


    • Andrew says:


      Thanks, but I don’t love that graph. First off, I don’t like the organization by day of month; second, I’d prefer a lineplot to get a sense of the scale of the changes. The heatmap doesn’t work for me. Don’t get me wrong—the graph isn’t bad, and it’s much better than a table of numbers (in particular, you can look right away and see Valentine’s Day and Halloween)—it just doesn’t quite get at what I’m interested in here.

    • Clark Andersen says:

      I like this graph a lot. I could envision providing more information in an interactive format, say displaying counts of individual days as you mouse over them, or making what is currently shown as the top of 3D bar plots which so that you could click-and-drag to view it from different perspectives. Fundamentally, the graph tells me pretty much everything I really want to know as-is.

      It might be fun to do some kriging and show it as a contour plot :)

      • Dave Backus says:

        I’m with you — this is great, much better than the table. If someone can do better, I’d love to see it.

  1. Eric Tassone says:

    I love the row effect apparent in the graph for the 13th day of each month! I knew people didn’t like 13th floors in buildings and 13th row seats on planes, but not having a kid (not scheduling a C-section?) on the 13th? I wonder if it’s powered by fear of Friday the 13ths or by a broader triskaidekaphobia?

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