WASHINGTON -- Minimum wage workers in a handful of states will be ringing in the new year with an automatic pay raise.

As Congress considers legislation that would boost the federal minimum wage, at least 13 states will be raising the wage floor on their own next week. They're led once again by Washington state, which will continue to have the highest state minimum wage in the nation, at $9.32 per hour.

A few cities and counties around the country will be raising their minimum wages as well, including San Francisco, which will set its at $10.74. San Francisco's base will no longer be the highest municipal minimum wage in the country, however, after voters in SeaTac, Wash., approved a ballot measure setting a $15 wage floor for an estimated 6,000 airport workers. The SeaTac minimum wage is set to go into effect Jan. 1, although it's currently being challenged in court.

Most of next week's increases will come courtesy of an inflation index. Ten states have tied their minimum wages to the index, guaranteeing that they rise with the cost of living each year. Other states, such as New Jersey and Connecticut, passed legislation in 2013 that will nominally raise their minimum wages. (California Gov. Jerry Brown signed legislation that will raise the state's minimum wage to $10 by 2016, but the first increase, to $9, won't come until July.)

The federal minimum wage prevails in the 31 states that don't currently mandate a higher one. The federal rate hasn't been raised since 2009, after the last of a series of increases signed into law by President George W. Bush took effect.

The federal minimum wage is not tied to an index, but Democrats in Congress, as well as President Barack Obama, have said that it should be. The minimum wage bill put forth by Sen. Tom Harkin (D-Iowa) and Rep. George Miller (D-Calif.) would raise the minimum wage to $10.10 and peg it to inflation. Obama, who previously suggested raising the wage floor to $9 and indexing it, has since gotten on board with the $10.10 proposal from Harkin and Miller.

The annual minimum wage raises in states and cities are routinely praised by low-wage worker advocates and panned by business-friendly groups. The Employment Policies Institute, a vocal critic of higher minimum wages, argued in a press release Monday that raises like the ones that will go into effect next week have "disastrous results for the most vulnerable jobseekers." Republicans on Capitol Hill have shown party-line opposition to the Harkin-Miller proposal, with leadership declaring a minimum wage increase a job-killer.

Most voters, however, don't seem persuaded by the critics' economic arguments, as they continue to approve higher minimum wages on the local level. The idea of raising the minimum wage tends to poll extremely well, including among Republicans who are not members of Congress. Most polls show that around two-thirds of respondents support raising the federal minimum wage. In a recent Washington Post/ABC News poll, half of Republicans who responded said it should be raised.

Here are the state and local increases that will go into effect next week, as compiled by the Employment Policies Institute: