Companies with more women board members achieved better financial results than businesses with fewer female directors, according to a group that promotes diversity in the workplace.

The report released Monday by New York-based Catalyst showed that return on equity at Fortune 500 companies with the most female board members was 53 percent higher than it was at companies with the fewest women directors. Return on equity, a company's after-tax income divided by book value, is a measure of how well earnings are reinvested.

Companies that understand diversity do better in the marketplace, said Catalyst, which focuses on expanding the opportunities for women in business.

Women on the board can be a sign that the company is more independent, innovative, and attuned to good corporate governance, the group said.

"What it means is that women need to be in the boardroom," said Ilene H. Lang, president of Catalyst, a nonprofit research firm. The relationship between female board members and a company's financial success "is not cause-and-effect, but there's a very strong link," she said.

In the survey, Catalyst divided Fortune 500 companies into four quarters by percentage of women on their boards of directors, then looked at their financial performance.

The group of companies with the highest average percentage of women directors did better. Their average return on equity was 14 percent.