I like looking at data. One thing I like is trends of names over time. Why? Because if you’re writing something, it makes sense the name of your character should match their age.

I like the Babynames.com site. It shows trends since 1910. (Though be careful. Enter names in the gray field right by the graph, not the darker one higher up the page — that way you’ll get results.) Here’s an example, using Jennifer, made famous for this kind of thing by the book Beyond Jennifer and Jason.

All right, but that’s not the only source. What about Social Security’s web site? (Go down to the “Popularity of a Name” box, and fill it in.) They’re using actual birth records as they come in.

The Social Security site shows a decline, just like Baby Names… but it’s much less sharp. What’s going on?

I had to think a while, and squint at the graphs, but I figured it out. In 1985, when the Social Security site tells us Jennifer was the 5th most popular name, the US birth rate (yes, it’s there, although not on the easiest site) was 15.461 births per 1000 people. In 2021, the most recent year listed, Jennifer was the 493rd most popular name, and the birth rate fell to 12.001 per thousand people — a drop of 22.4%.

Why is this important? Well, the Babynames chart is showing how many kids get a name. The Social Security chart shows the rank of the name among all others.

So while Jennifer was becoming less popular among names, people were having fewer babies in the first place.

Double-whammy. And that’s why the graph looks so much more spiky.

Yes, probably few people care. But it was a fun puzzle for me.