Thanks to a new quota law, some 25.1 percent of directors on the boards of the 17 top French companies are now women, a higher ratio than in the United States, a new study showed.

"France has raised the bar for other countries interested in opening up corporate board rooms to women," said Irene Natividad at the Washington-based Corporate Women Directors International (CWDI) which conducted the study.

The study shows that France has overtaken the United States in placing women on the boards of the world's 200 largest companies. 

The average percentage of female directors among Fortune Global 200 companies, the world's largest by revenues, came to a modest 15 percent. Thanks to a new French quota law, the number of women directors in 17 top French companies equated to 25.1 percent, while only 20.9 percent of board members were women at the 57 largest US companies.

In a similar study released in late 2011, France beat a timetable set by the quota law taking effect in January of that year, that requires publicly listed companies to make 40 percent of their directors women by 2017.

The law set a halfway point of three years to reach 20 percent, and France had 20.1 percent. That marked substantial progress from 7.2 percent representation in 2004, when the CWDI first tracked the data.

"The dramatic increase in the number of women now serving on the boards of French companies shows that it is possible to do this at a quicker pace, as long as there's a plan to do so," Natividad said.

Norway initiated the board room quota drive in 2003 and reached its 40 percent mandate in 2008.

Five other European countries now have government quotas on female directors in public companies: Belgium, Iceland, Italy, the Netherlands and Spain. Outside Europe, Malaysia is the sole country with such a quota.

Ten other countries have quotas for women on the boards of government-owned companies, bringing to 18 the number of countries with some kind of quota.

The improved numbers worldwide also were driven by the inclusion of gender or board diversity language in the corporate governance code in several European countries, the CWDI said.

Finland led that drive and now has 22 percent of board seats held by women, in an initiative that has spread to other continents, the group said, calling it "a very popular strategy for countries wanting to avoid quotas."

"There are now 17 countries who have adopted this initiative," the research group said.

The data made clear that government quotas and gender diversity recommendations spurred women's acceptance to the boardroom.

"Quotas work," said Natividad. "Inserting gender diversity into corporate governance codes works.

"What doesn't work is assuming that women will rise to board seats 'naturally,' and therefore do nothing."

The world's top three economies -- the United States, China and Japan -- are home to 104 of the Fortune 200 companies, but had the lowest percentage increases in women-held board seats.

"None of these countries have concerted proactive strategies to improve the numbers of women directors in their respective countries," the CWDI said.