At an Annapolis rally to raise the minimum wage last month, the crowd chanted "10-10," a refrain that refers to the $10.10 hourly rate proposed by Gov. Martin O'Malley.

Two weeks later during President Obama's State of the Union speech, the president said he would raise the minimum wage to $10.10 for federal contractors. He called on state lawmakers, mayors and governors to raise local wages if Congress would not act.

As Maryland lawmakers are scheduled to debate next week whether to vote for the biggest wage increase in Maryland history, some may be wondering why $10.10?

Why not a round number? Or a $3 increase to the current federal wage of $7.25?

Many advocates point out that the minimum wage had its strongest buying power in 1968, thirty years after it was first enacted. In 2014 dollars, the $1.60 minimum wage of 1968 would be worth $10.74 today if adjusted for inflation using the Consumer Price Index.

(Some conservative groups argue that another measure of inflation known as the Personal Consumption Expenditure gives a better estimate of a wage's buying power in today's dollars. A recent Heritage Foundation report said a 1968 wage would translate into something closer to $8.28 today.)

Neither explanation gets us to $10.10, the figure in a bill proposed by Democratic senators in Congress and adopted by advocacy groups across the country.

Stacey Mink, communications director of the Raise Maryland coalition, said advocates want minimum wage to be high enough so that families who rely on it don't live in poverty. They hope to get it above $10 to make that possible, effectively giving raises not just to $7.25 workers but to everyone who makes less than $10 an hour.

In early 2013, national advocates suggested raising the wage to $10 by 2015. This year, accounting for a little inflation and the weakening value of the minimum wage, they added a dime and suggested phasing it in by 2016.

The fact that the symmetrical dollar amount translates into an easy-to-chat slogan may have nothing to do with it, Mink said, "but it certainly doesn't hurt."