MSCI Inc. isn’t usually a name that springs to mind when one thinks of the most powerful players in the global equity market.

The New York-based index compiler doesn’t have BlackRock Inc.’s trillions under management, Morgan Stanley’s army of financial advisers or UBS Group AG’s storied history. At $7.7 billion, MSCI’s market value is too small to crack the top 300 of global financial firms, and its payroll of about 2,700 pales in comparison to that of Franklin Resources Inc., one of America’s biggest fund managers.

Yet thanks to the surging popularity of passive investing, MSCI and a handful of its rivals -- including FTSE Russell and S&P Dow Jones Indices -- are quietly replacing the giants of money management as the most important arbiters of where the world’s stock investments flow. The average proportion of equity funds in the U.S., Europe and Asia that mimic index providers’ security and country allocation decisions has doubled over the past eight years to about 33 percent, according to Morningstar Inc.

That growing heft was on full display this year in China, where authorities enacted some of the nation’s most far-reaching market reforms in hopes of gaining entry into MSCI’s global stock gauges last month. The country’s ultimately unsuccessful campaign cemented the index compiler’s status as one of the few companies worldwide with the ability to influence the policy decisions of China’s ruling Communist Party.

“They have an awful lot of power,” said George Cooper, the chief investment officer at Equitile Investments Ltd. in London. “Fund managers and investors are slavishly following these indices.”

Index providers aren’t stock pickers in the same sense as active money managers, who attempt to beat the market by choosing only the best securities. Most of the criteria used by MSCI and its peers are measures of investability, such as market capitalization and daily volume, rather than anything purporting to generate above-average performance.

The index firms say they’re merely channeling the collective feedback of their clients, who include active investors using benchmarks to gauge relative performance and passive managers who need them to deliver the market return.

“International investors will not blindly follow any decision we make,” Mark Makepeace, the London-based chief executive officer of FTSE Russell, said in an interview.

But there is a degree of subjectivity that goes into developing a benchmark index, particularly when deciding on contentious issues, such as which countries to classify as developed, emerging and frontier.

MSCI’s decision to leave domestic Chinese equities out of its global gauges in June surprised many forecasters, while its upgrade of Pakistan to emerging-market status the same month sent shares in Karachi surging to a record -- a sign that investors had failed to price in the move. MSCI didn’t respond to requests for comment for this story.