President Obama and his Democratic allies are hoping to win women voters by a large margin -- and part of that strategy involves making equal pay a big issue. 

"If you do the same work as a man, you ought to be paid the same wage as a man," the president said at a reception honoring women from around the world in March of last year. 

Research from the Bureau of Labor Statistics indeed suggests women on average make only 77 cents for every dollar earned by men. 

Those numbers, however, could represent an apples-to-oranges comparison. The stats compare the pay of all women as a group against the pay of all men as a group, without considering lots of differences. Some analysts are now producing research that suggests the pay difference might be tied more to the jobs men and women each choose than their gender. 

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