Q. I've been told that Social Security keeps track of the names of babies born in the United States each year. What are the most popular baby names?

A. In 2011, the top 10 male names were Jacob — at No. 1 — followed by Mason, William, Jayden, Noah, Michael, Ethan, Alexander, Aiden and Daniel.

The 10 most popular female names, in order, were Sophia, Isabella, Emma, Olivia, Ava, Emily, Abigail, Madison, Mia and Chloe.

See also: Website lets you keep track of popular names.

Social Security has those stats because most parents apply for numbers for babies as soon as they're born. In 2011, there were 3.9 million such applications — 2 million boys and 1.9 million girls.

Keeping track of names can get a bit more complicated when twins are involved. In 2011, the most popular names for female twins were Olivia and Sophia (there were 50 such pairs). For male twins it was Daniel and David (58 pairs). And for boy-girl twins, it was Mason and Madison (50 pairs).

Names wax and wane in popularity, of course. A century ago, Social Security says, Mary, Helen and Dorothy were the top three names for girls, while John, William and James held the spot for boys. In 1981, Michael, Christopher and Matthew took control of the top slot for boys' names and kept it for 14 years. Jennifer, Jessica and Amanda were the most popular girls' names in 1981 and two consecutive years after.

There's no requirement that a newborn get a Social Security number right away, but, with the number figuring in so many official documents such as tax returns and bank account applications, it's a good idea not to wait.

Parents who apply for a birth certificate for a newborn will be asked whether they want to get a Social Security number as well. The state agency that issues the certificate will forward the baby's information to Social Security, which will mail a card to the parents.

Stan Hinden, a former columnist for the Washington Post, wrote How to Retire Happy: The 12 Most Important Decisions You Must Make Before You Retire. Have a question for the Social Security Mailbox? Check out the archive. If you don't find your answer there, send a query.

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