President Barack Obama's proposal to increase the U.S. minimum wage by 24 percent faces long odds in Congress, where Republicans took aim at it minutes after the State of the Union address. That might not matter: beyond Capitol Hill, some states took action long ago.

Nineteen states and the District of Columbia already require employers to pay more than the $7.25 an hour required by federal law, according to the U.S. Labor Department. At least eight more, including New York and New Jersey, are considering legislation to join them. On Jan. 1, Washington state, home to the highest minimum wage in the nation, raised its floor to $9.19, more than the $9 an hour proposed by Obama.

The patchwork of laws has offered new insight into the effect of higher wages on jobs. Some economists are challenging the traditional precept that as the price of something goes up, demand goes down, at least when it comes to labor.