That is the message from Mark Makepeace, the chief executive of FTSE Russell, the index provider whose products are now used to track roughly $12.5 trillion (9.65 trillion pounds) as clients pour money into so-called passive products.

Some fear the rush of cash could destabilise markets by removing humans from trading decisions.

But in an interview on Monday, Makepeace said the bulk of the money following various FTSE Russell indexes is the $9.7 trillion in active funds whose managers use his company's products for benchmarking or to make their own trading decisions.

While he once shared the conventional wisdom that markets could be distorted if half of all assets were held passively, Makepeace called that standard an "old way of thinking about indices," as they are put to new uses by active managers. Demand is also growing as investors use indexes in new areas, such as fixed-income.

"Big investors will start to look at the market in much more holistic ways," Makepeace said by telephone.

Makepeace said FTSE Russell aims to grow the amount of money following its various products by about 60 percent to $20 trillion within three years.

FTSE Russell is part of London Stock Exchange Group. The firm and its rivals including MSCI Inc have found their products in demand from big asset managers and pension funds riding a boom in low-cost investing.

Passive products like the Vanguard Russell 3000 Index Fund aim to track the performance of benchmarks such as the Russell 3000, a broad measure of U.S. stocks.

Net deposits to passive funds were $638 billion for the 12 months ended March 31, according to Morningstar, while active funds had net withdrawals of $310 billion over the same period, excluding money funds.

The divergence has led to angst.

"If everybody indexed, the only word you could use is chaos, catastrophe," Vanguard Group founder Jack Bogle said on Saturday in an interview with Yahoo Finance.

Still, Bogle and others see no sign of a passive slowdown. Makepeace said he expects to see more consolidation as costs fall for investors.

Separately, Makepeace also noted moves by Saudi Arabia to reform its economy, which could make it more attractive to foreign investors.

"That market is opening up very quickly and therefore I would not be surprised if Saudi beat China to be included in emerging market indexes," he said.

(This story has been refiled to correct fourth paragraph describing amount of funds following indexes.)

(Reporting by Ross Kerber, editing by G Crosse)

By Ross Kerber