Other generational sequences in recent announcements also mirror the history of common names: Mary–Jennifer–Madelyn; Mary–Ashley–Emily; Mary–Cora–Elizabeth.

In the tradition of treating statistical trends as horse races, I imagine that there is one person named Mary, who is constantly falling behind: first behind Linda, then Lisa, Jennifer, Ashley, Jessica, and so on, all the way to Isabella and now Sophia.

But that's not how it happens—it just looks that way because of the amazing regularity in human behavior, which produces an orderly succession of names. Incredibly, out of 1.7 million girls' names recorded by the SSA in 2011, I was able to predict to within 87 how many would be named Mary. By simply taking the number born in 2010 and subtracting the 5-year average decline, I predicted 2,584 would be born; the actual number was 2,671 (an error of 3.3 percent).

Somehow, out of the millions of individual decisions parents make, they produce steady trends like this. (If you're as amazed as I am, consider a career in sociology! If not, please bear with me.)

So what does the Mary trend mean? First, it's the growing cultural value of individuality, which leads to increasing diversity. People value names that are uncommon. When Mary last held the number-one spot, in 1961, there were 47,655 girls given that name. Now, out of about the same number of total births, the number-one name (Sophia) was given only 21,695 times. Conformity to tradition has been replaced by conformity to individuality. Being number one for so long ruined Mary for this era.

Second, America's Christian family standard-bearers are not standing up for Mary anymore. It's not just that there may be fewer devout Christians, it's that even they don't want to sacrifice individuality for a (sorry, it's not my opinion) boring name like Mary. In 2011 there were more than twice as many Nevaehs ("Heaven" spelled backwards) born as there were Marys. (If there is anything more specific going on within Christianity, please fill me in.)

I'm not here to give advice to people who want to bring back the "traditional family." But if I were I would recommend putting your names where your tradition is—and producing some more Marys.

There are precedents for bringing names back. My simple linear prediction method fails once in a while, when a name's trend turns around. The greatest example is probably Emma. Emma was at number three when the SSA records begin, in 1880. She fell almost down to #500 by the 1970s. But after a decade of uncertainty she began a fantastic run, finally reaching number one in 2008.

I don't know (yet) what makes a name turn around like that. Why Emma and not Mildred or Bertha, both former top-10s who fell into oblivion? But if any name has a chance for a similar resurgence, it might be Mary, at least as long as Christianity keeps hanging around.

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