It has been one of the consistent cries, mainly of Democrats, over the past seven years. It goes something like: Women earn 77 cents on the dollar (or pick your amount) for doing the same work as a man (or pick your description). But critics say the wage gap is more fiction than anything. What are the facts?

Our PolitiFact Sheet on the gender wage gap explains.​

THE TOP LINE

The first thing you can do to protect yourself against misusing the 77 cents statistic is simple: Listen carefully. Slight differences in wording can drastically alter the accuracy of a claim about the wage gap.

Here’s what we mean: In his 2012 re-election run, an ad for President Barack Obama claimed "Women (are) paid 77 cents on the dollar for doing the same work as men." That rated Mostly False .

But Obama retooled his words in his 2014 State of the Union address, saying women "still make 77 cents for every dollar a man earns." That rated Mostly True.

The difference in Obama’s two statements is subtle but important. The 77-cent figure derived from a federal government measure does not apply to men and women who do the same job. Instead it refers to the average disparity between what men and women earn, period. All women’s earnings compared to all men’s earnings.

Still, even when presented more accurately, the statistic comes with a raft of caveats.

THE DETAILS

Credible federal data on the wage gap comes from the Census Bureau and the Bureau of Labor Statistics. These agencies measure wages differently, so their numbers are not identical.

The Census Bureau tracks annual wages for all male and female workers regardless of occupation. In 2012 , women who worked full-time, year-round made 77 cents for every dollar earned by men. Data for 2013 show women who worked full-time, year-round earned $39,157 compared to $50,033 for men — or about 78 percent of men’s earnings, which is not a statistically significant jump.

The Bureau of Labor Statistics instead uses weekly earnings of workers in full-time wage and salary positions from the Census Bureau’s monthly Current Population Survey of 60,000 households. In 2013, women’s wages were 82 percent of men’s wages, or $706 versus $860, in line with recent years. Unlike the Census figure, the BLS method does not account for self-employed workers, though it does include people left out of the year-round wage measure, including teachers, construction workers and seasonal workers.

And just to make things more complicated, if you measure by hourly earnings, you get a different figure. Hourly earnings from BLS show a smaller pay gap, accounting for part-timers who are more often women and paid less than salaried counterparts. In 2013, women earned median hourly wages of $12.12, or 87 percent of the median $14 an hour for men. (This measure excludes salaried workers.)

Which method is best? Experts and advocates disagree.

Heidi Hartmann, president of the Institute for Women’s Policy Research , told PolitiFact in 2012 that the measure of annual wages is "most traditional," as it goes back the furthest and doesn’t exclude salaried workers.

But the Federal Reserve Bank of St. Louis prefers working with hourly wages because women work fewer hours than men, "which would make a gap in weekly earnings between the two groups substantial even if their hourly wages are the same."

THE EFFECT ON YOU

It is illegal, under Title VII of the Civil Rights Act of 1964, for employers to discriminate against employees based on gender, as well as race, color, religion or national origin (and in some states, sexual orientation).

Experts say outright discrimination isn't the only explanation for the wage gap. The wage gap for women shrinks and expands depending on a number of factors.

One reason for the wage gap, experts say, is what is called "occupational segregation." Women more often than men work in jobs that pay low and minimum wages . The Institute for Women’s Policy Research says more than twice as many women than men have jobs with full-time wages under the federal poverty threshold for a family of four.

Still, a wage gap exists for the most popular jobs pursued by women.

The institute researched pay parity for the top 20 occupations for women in 2011 using median weekly earnings, finding that women were behind in almost every category (except for bookkeeping, accounting and auditing clerks, where there was basically no gap in pay). Occupations with the widest difference in pay were accountants (77 cents) and financial advisers (66 cents), while nurses (96 cents) and cashiers (90 cents) were closer.

A wage gap exists in every part of the United States, PolitiFact Georgia found , ranging from a low of 66.6 cents in Wyoming to a high of 90 cents in Washington, D.C., in 2010. But if broken down by narrow groups, research shows single, childless women in their 20s in major metro areas outearned male peers, specifically in Atlanta by 21 percent and by 12 percent in Los Angeles.

THE BIG PICTURE

Just before Obama took office in 2009, the Department of Labor released a study because, as a deputy assistant secretary explained it, "The raw wage gap continues to be used in misleading ways to advance public policy agendas without fully explaining the reasons behind the gap." The study by CONSAD Research Corp. took into account women being more likely to work part-time for lower pay, leave the labor force for children or elder care, and choose work that is "family friendly" with fuller benefit packages over higher pay. The study found that, when factoring in those variables, the gap narrows to between 93 cents and 95 cents on the dollar.

"The raw wage gap should not be used as the basis to justify corrective action," said Charles James, the deputy assistant secretary. "Indeed, there may be nothing to correct."

Still, a study by the American Association of University Women controlled for a number of factors, including college major, occupation, age, geographical region and hours worked, and found a persistent 7 percent wage gap between men and women a year after graduating college.

The report explored discrimination and reluctance among women to ask for raises as reasons for the remaining gap, though those factors are hard to measure.