The federal minimum wage — $5.15 an hour — has not changed since 1997. Since then, minimum-wage earners have lost 17 percent of their purchasing power to inflation. Supporters of increasing the rate say it would lift many Americans out of poverty, but business groups say an increase would hurt the working poor because it would cause companies to lay off low-wage workers. In any case, they say, many minimum-wage earners are middle-class teens earning pocket money, not poor adults. Attempts in Congress to raise the minimum wage failed this year, but perennial sponsor Sen. Edward M. Kennedy, D-Mass., says he will try again next year. Seventeen states and Washington, D.C., now have higher minimum wages than the federal level, and 130 cities and counties have so-called living-wage laws requiring public contractors to pay significantly higher wages. Nevada and Florida recently passed minimum-wage ballot initiatives, and more state battles are looming.