These charts are from the Economic Policy Institute. They show the gender wage gap between men and women in the United States. The top chart shows the wage gap from about 1979 until the present. In 1979, women only made about 62.4 cents for every dollar a man made doing equal work.
That has gotten a little bit better now, with women making 82.7 cents for every dollar a man makes. Part of the decrease in the gap is because women are paid a bit more now, but sadly, part is also because the wages for men have decreased.
The second chart shows that the wage gap exists among all income levels. In fact, it is a little less among the lowest 20% of the population -- mostly because the minimum wage applies equally to men and women.
The other three charts show that the gender wage gap persists among all ages, education levels, and races/ethnicities.
This must be fixed. There is no legitimate reason why women should be paid less than men for equal work. Unfortunately, it won't be fixed as long as the Republicans stay in power in the Congress. They have killed every effort to establish equal pay in the past, and are sure to do it in the future.
On the other hand, the Democrats have tried for years to pass laws to abolish the gender wage gap. And if they are able to control Congress after this election, you can be sure that they, in conjunction with President-to-be Clinton, will fix this inequality.