One of the themes of this election season has been the Wall Street analysts who expect the U.S. economy to do better under Hillary Clinton, who would be the nation’s first female president, than under Donald Trump. Similar bets about the value of female leadership are being made in the stock market.

The SPDR SSGA Gender Diversity Index exchange-traded fund SHE, +1.13% , launched earlier this year, has attracted attention from those who want to play its central strategy: that companies with a high representation of women in the executive ranks outperform their male-dominated peers. But while the fund was created to support the cause of corporate gender diversity, performance data shows support for the fund’s thesis, meaning investors wouldn’t just be making a moral statement, but could also get a financial benefit for their position.

“We see an opportunity to invest in companies that are best utilizing female talent, especially at the senior executive and board level,” wrote UBS in an Aug. 29 note that specifically referenced the ETF. “Available evidence is supportive of a positive impact of greater gender diversity on company profitability and stock price performance. The reasons for these results are attributed to improved decision making due to greater diversity of perspective and skills.”

According to MSCI Research, companies with strong female leadership generated a return on equity of 10.1% a year, compared with 7.4% returns for those without, though it added that “we couldn't establish causality.” MSCI defines strong leadership as a company with at least three female board members, or both a female chief executive and a female board member, or a board where the percentage of women is above average. While 73.5% of U.S. companies have at least one female director, according to MSCI, just 20.1% have three or more.

“Three women may constitute a critical mass to allow women to contribute more equally to group decision making,” MSCI wrote in a November research report. “We also found that companies lacking board diversity suffered more governance-related controversies than average.”

The SSGA fund evaluates the 1,000 largest companies for the ratio of women on their boards or in executive positions, which it defines as a senior vice president or higher.

“We all agreed that it would be great to include some measure of the number of women who actually run the component companies from day to day. We capture broad participation by women across the entire executive level, looking at all kinds of senior management,” said Jenn Bender, director of research, global equity beta solutions at State Street Global Advisors.

The problem with a more narrow view, she added, “is that having a single female board member can be, for lack of a better word, tokenism. Just having one doesn’t represent diversity.”

State Street Global Advisors (SSGA) is one of the biggest names in the ETF industry, having issued such asset-class-defining products as the SPDR S&P 500 ETF SPY, +1.01% —the largest ETF by assets—and the SPDR Gold Shares ETF GLD, -0.48% . The Gender Diversity fund marks the first time it has self-indexed one of its funds, meaning it created the benchmark that the ETF tracks.

“We were inspired by our work with Calstrs (the California State Teachers’ Retirement System), who was very committed to trying to create some kind of investment vehicle where people who cared about gender diversity could go,” Bender said.

The ETF isn't the first investment vehicle designed to play this strategy. A mutual fund, Pax World Global Women’s Equality Fund, was launched in 1993. In 2014, it merged into Pax Ellevate’s Global Women’s Index Fund PXWEX, +0.37% .

Since its March 8 launch, the gender-diversity ETF is up 7.1%, compared with the S&P 500’s 6.9% rise. The Pax fund, whose benchmark is the MSCI World index 892400, +0.43% , is up 4.3% over that same period. Over the past eight years, the Pax mutual fund has averaged an annual gain of 1.1%, below both the MSCI World index’s average annual gain of 3.78% and the S&P’s average gain of 6.4%.

Because the gender-diversity ETF invests across sectors and is market-cap weighted—Pfizer Inc. PFE, +0.63% , PepsiCo Inc. PEP, +0.69% , 3M Co. MMM, +0.60% , Starbucks Corp. SBUX, +0.07% , and Texas Instruments Inc. TXN, +1.21% are among its top 10 holdings—the ETF is highly correlated to the broader market. Moreover, market participants say the short period since the ETFs inception, and the generally low volatility of the broader market in recent months, has further limited the potential for significant price divergence between the fund and the S&P 500.

Bender cited the Ellevate fund’s aim as an inspiration for the ETF, which also was created to be “more accessible to average investors, and more cost efficient.” The ETF has an expense ratio of 0.2%, compared with the mutual fund’s total expenses of 0.9%.

The SPDR gender-diversity ETF has about $274.4 million in assets under management, the most of any ETF launched this year, according to ETF.com. However, $250 million of the inflows it has seen in 2016 came in the form of seed money from Calstrs, suggesting it has yet to gain much broader acceptance by investors. The fund also has been thinly traded since its inception. Over the past 30 days, only about 1,000 shares have traded hands daily, on average.