Most popular baby names ... for now. Beware, Sophia.

The most popular baby names in the US are Sophia (for girls) and Jacob (for boys), according to the Social Security Administration's new list of top 2011 baby names. But if history is any guide, it won't take long before Sophia goes the way of Barbara (No. 764).

We wrote Monday about how the Social Security Administration had released its most popular baby names of 2011, with Sophia leading the pack for the girls and Jacob holding steady as the country’s No. 1 boy name.

Today, we take a peek at what’s happened to some of the other top names from the past few decades. And it turns out that Sophia, Isabella, and Emma should be afraid. Very afraid.

As we mentioned before, the administration keeps a database of American baby names going back to 1880.  A user can browse the names by popularity or year, which can turn into a mesmerizing look at American groupthink – or at least pop culture creep.

Sociologists, psychologists and those specializing in onomastics (the study of names) have theorized why it is that parents – even those scouring baby name books for the perfect, unique moniker – tend to end up as part of a country-wide trend.

Names, the prominent theories say, are typically driven by fashion. And while many parents today might be trying to pick a “unique” name (a new trend in and of itself), they usually don’t want something totally outlandish. So they’ll try to make a little twist on an existing popular name; for instance, turning “Emily” (No. 1 from 1996 to 2007) into “Emma.” 

The thing is, everyone else is doing the same. ("Emma" went from No. 53 in 1996 to No. 1 in 2008). Because you can’t actually be fashionable and unlike all the others.

This is also why a name that sounds culturally “high class” quickly “filters down” in socio-economic standing. (“Freakonomics” authors Steven Levitt and Stephen J. Dubner wrote about this.) As the masses decide to name their children, say, "Chloe" (today’s No. 10, up from No. 853 in 1982), Chloe becomes, by definition, less elite.

If parents really wanted unique, they’d pick one of those names that they heard every day in elementary school.  “Jessica” – No. 1 or 2 from 1981 to 1997 – has dropped from No. 11 in 2001 to No. 120 in 2011.  “Jennifer,” top ranked from 1970 to 1984 is now at spot 134.

But these are names that parents already have. Or that they associate with friends, enemies, frenemies, sisters, whomever, and don’t want to revisit. This is, we suspect, what has happened to Barbara, Carol, Deborah, et al. – top names from the 50s.

Barbara sat in the top 10 baby girl names from 1927 to 1958. Today? She’s No. 764.

Carol? Top 10 from 1936 to 1950. Today, No. 972.

Deborah, who enjoyed top 10 standing from 1950 to 1962? Now No. 808.

Take heed, Isabella. (No. 2 this year, already on her way down.)

Jacob and William (No. 1 and 2) don’t have to worry quite as much. Boys names tend to have less variation.  Sixth-ranked “Michael,” for instance, held the No.1 or 2 spot from 1954 to 2008. And he’s never dipped below No. 60 in the last 100 years.