Among the causes First Lady Michelle Obama has championed during her time in the White House is improving the lot of girls and women worldwide. About a year ago, Obama helped kick off Let Girls Learn, an interagency effort focused on educating adolescent girls.

"Studies from the World Bank show that one extra year of secondary school can increase a girl's future income by 15 to 25 percent," Obama said in an interview with a U.S. Agency for International Development publication . "And we know that when girls are educated, they are less likely to contract HIV, more likely to delay childbearing and vaccinate their children, and have lower maternal and infant mortality rates. Research even shows that sending more girls to school can boost an entire country’s GDP."

We’ve seen that claim about educating girls and a rising GDP before. Is it true?

Largely, yes. Research does show that a higher percentage of girls in school correlates with a higher gross domestic product. But those findings are much more limited than many people understand.

Behind all the research, there’s uncertainty about whether a stronger economy leads to more girls in school, or if more girls in school leads to a stronger economy.

No single rule applies everywhere. A stronger economy, for instance, provides both the resources and incentives to educate more women, who go to school, earn more and boost the economy a little higher. But it doesn’t always work that way. In the Middle East and North Africa, more women might be educated but for social and religious reasons, they can’t work, or must work in jobs that don’t fully reward their level of education.

And the biggest sticking point is that what’s been called the "girl effect" seems to be much stronger in middle-income countries. For poorer nations, the effect is more muted.

A few key studies and cautions

The White House press office backed up the First Lady’s claim by citing policy reports that declared that educating girls and young women would boost a country’s economy. One from the World Bank said "By effectively educating more women -- that is, providing more women with a high-quality education -- more will enter the labor market, and the economy will show the favorable results."

Those reports didn’t actually give the underlying research, so we’ll cover the highlights.

• A 2009 article in the journal Feminist Economics compared regions of the world and measured gender gaps in both education and employment. That’s worth noting because, while the two generally go hand-in-hand, they are separate. You can educate girls, but if companies won’t hire them, a lot of the economic benefit is lost.

This study’s bottom line was that between 1960 and 2000, East Asia’s growth rate was .9 percent higher than the region of the Middle East-North Africa. The difference was due to the higher fraction of girls in school in East Asia.

• A 2011 World Bank study took 14 countries and teased out what would happen if every girl finished whatever level of school she was in -- either primary or secondary. Not surprisingly, the economic impact depended hugely on a country’s starting point. India and China, for example, had very low rates of girls not completing school, while on the opposite end, places like Burundi and Senegal had dropout rates over 80 percent.

So the study found that getting girls and young women to complete a given level of schooling added a "barely noticeable" amount in India and China, while in the other countries, researchers predicted a hefty rise.

One important contribution of this research is it factored in the diminishing returns of educating more women. When more people hit the job market, it tends to drive wages down. There’s still a net gain, but in this study, earnings could be about 20 percent less than you might expect.

Tuck that point away and keep it in mind for the next landmark analysis on our list. It provided advocacy groups with a talking point that has gone viral.

• In a 1999 World Bank paper Gender inequality, income and growth: Are good times good for women?, economists David Dollar and Roberta Gatti worked with data on 100 nations. The finding that gained the most traction was that "in the countries with higher initial education, an increase of 1 percentage point in the share of adult women with secondary school education implies an increase in per capita income growth of 0.3 percentage points."

That might seem like a simple equation, but it actually makes two points that are often overlooked.

The economic growth took place only in middle-income countries that already had a higher rate of educating women. "For the poorer half of the observations, there is no relationship between female attainment and income," the authors wrote.

The other generally ignored element is that the 1 percent increase in educated women applies to completing secondary education. Simply putting more girls in classrooms at any grade level wouldn’t necessarily deliver the same results. You have to get the girls all the way through high school.

Specifics are important when measuring education gains

Here’s where many organizations, including USAID , get into trouble. They say -- right now on their website -- that "if 10 percent more girls attend school, a country’s GDP increases by an average of 3 percent."

That statement has three flaws. First, it treats all nations the same, whether they are low income or middle income. Second, it treats all education the same, whether it’s primary or secondary.

Perhaps most troubling is it scales up the original equation by a factor of 10.

Dollar, now a senior fellow at the Brookings Institution, told us that doing that "is a bit risky."

"You would expect diminishing returns," he said.

Which takes us back to that 2011 World Bank study we tucked away. It predicted wages would be about 20 percent lower than you would expect. Less money in women’s pockets means less economic activity, and less economic growth.

Our ruling

Michelle Obama said that research shows that sending girls to school can boost a country’s entire economy. That’s a fairly broad statement and broadly speaking, it’s accurate. Research from economists at the World Bank and elsewhere suggest that it’s possible that educating more girls produces a stronger economy.

But researchers can’t say whether it’s the education of girls that leads to growth, or the growth that leads to more education of women. Plus, women can hit roadblocks in the job market even if they are educated.

The research shows that, too.

Obama’s statement is accurate but it needs additional information. We rate this claim Mostly True.