Much of the basis for such optimism, though, does not come from the U.S. The percentage of board seats of S&P 500 companies held by women hasn’t budged much since last year.

Among the findings from Catalyst’s report, released Tuesday:

• About 19.2 percent of the board seats of S&P 500 companies are held by women, which is about even with last year.
• The U.S. is tied with Australia for tenth place among the 20 developed nations that Catalyst surveyed.
• In general, European countries are doing quite a bit better than the U.S.: 35.5 percent of board seats at Norwegian companies are held by women; 29.9 percent of Finnish board seats are held by women; and in France, women hold 29.7 percent of board seats.
• Some countries have seen a dramatic growth in the number of women on boards. In the United Kingdom, the number stands at 22.8 percent, which is not that different from the U.S. figure. But as recently as 2011, only 12.5 percent of board seats in the U.K. were held by women. That’s a big change in a relatively short period of time.

“When you look at the countries in Europe, this is something people are thinking about and the business impact it can have,” says Brande Stellings, vice president of corporate board services for Catalyst, a not-for-profit that works to advance professional women in the workplace.

As other countries move more aggressively to get more women on boards – Norway, for example, was the first nation to mandate a quota for women on boards – U.S. companies will increasingly look like laggards, and face pressure to change as well, says Stellings

Brad Stadler, a managing director with recruiting firm True, who often engages in board searches for tech companies about to go public, says his clients almost always ask him to present a diverse slate of candidates. Because his client’s requirements are so specific, Stadler says, he’s not always able to do so.

But he also sees change coming: “There are definitely more women candidates for the functional searches we’re doing,” he says. “We’ve placed a number of women in COO and CEO positions, and as functional leads. That has increased over the last several years, and as those companies become successful and grow, I think that will translate into more diverse boards.”

While the U.S. doesn’t compare well to Scandinavian countries, there are plenty of countries that Catalyst found to be doing worse. Within Europe, Portugal has the lowest percentage of women on boards, at 7.9 percent. Ireland stands at 10.3 percent, and Germany, which is about to implement its own quotas, is at 18.5 percent.

Within the Asia-Pacific region, Australia fares the best, with 19.2 percent of board seats held by women. Japan does by far the worst, with only 3.1 percent of board seats held by women. Hong Kong and India come in at 10.2 percent and 9.5 percent, respectively.

There is some good news coming out of the U.S., however, in what Stellings refers to as “the zero list,” or the companies that don’t have even one woman on their board of directors. Last year, there were 50, a number that hadn’t budged in two years. This year, there are only 18.

Because last year’s study was based on the Fortune 500, and this year’s uses the S&P 500, “We can’t make a direct comparison,” says Stellings. “But I do think we can say it’s no longer acceptable to have zero women on a board of directors.” She finds that encouraging, yet cautions, “I just hope we don’t get stuck at one, and that one becomes the new zero.”

Overall, increasing the percentage of women on a board of directors has been linked to improved financial performance, corporate social responsibility, and an increased number of women in other high-level positions. Corinne Post, an associate professor of management at Lehigh University, says those effects vary greatly by nation.

With Kris Byron, an associate professor of management at Syracuse University, she looked at 140 studies of board performance in 35 countries, and says that overall, having more women on a board of directors does improve a company’s financial performance. “With more women on boards, a wider range of insight, perspectives, and experiences are brought to bear on the issues a board faces,” she says. “It improves how a board makes decisions.”

But she also says having more women on a board of directors does the most for a company’s financial performance in countries with stronger shareholder protections. “If you can be sued for misconduct, that would incentivize a board to pay attention to what women are saying,” says Post. Of the countries studied by Catalyst, shareholder protections are the weakest in the Netherlands, according to a World Bank ranking, where women hold 21 percent of board seats. They’re the strongest in the U.S, although Singapore and Malaysia (not studied by Catalyst) rank higher.

The other factor that Post and Byron found to have a bearing on the effect of women on boards is a country’s overall gender parity. In countries with a higher level of equality between the sexes (as measured by the World Economic Forum), having women on boards has a stronger effect in raising a company’s share price. If a country is ranked extremely low in gender parity, a higher percentage of women on boards may actually hurt the share price, although Post is not certain why this is.

In general, the Scandinavian countries are the ones with the highest gender parity, according to the World Economic Forum, and they’re also the countries that generally have the most women on their boards. The World Economic Forum says the U.S. ranks 22nd in gender parity, between Canada and Mozambique.

“There’s this notion that if you stick women on boards it’s like pixie dust, and performance increases,” says Post. But globally, she says, “holding boards directly accountable really makes a difference.”

Learn more about women on international boards from Fortune’s video team: