The latest data show that thanks to investors putting a lot of money into stocks, bonds, commodities and alternative funds, the asset size of U.S. ETFs reached $10 trillion, a new record.

This year, as the Federal Reserve cut interest rates and pushed up the stock market, investors are increasingly withdrawing funds from the money market to return to the stock market. Wall Street ETFs have attracted about $691 billion in capital so far this year, according to statistics.

Amrita Nandakumar, president of Vident Asset Management, said: “ETFs now provide access to virtually every asset class and strategy that was once only available to the world's most sophisticated institutional investors. It's a testament to how democratized ETFs have made investing.”

The $583 billion SPDR S&P500 ETF Trust, the first and largest ETF to track the top 500 U.S. publicly traded companies, is up 21% year-to-date, well above the average annual growth rate of 6.8%.

In addition, the second largest ETF, the $543.2 billion Vanguard S&P500 ETF, has attracted an even bigger $45.2 billion this year. These two ETFs account for more than 10% of the ETF market.

Jillian DelSignore, global head of investor distribution strategy for Nasdaq's Global Index Group, said, “ETFs are becoming the tool of choice for investors.”

Since the first ETFs were introduced more than 30 years ago, the asset class has seen a steady rise in capitalization. Over the past few years in particular, investors have increasingly favored more liquid and tax-advantaged ETF products. Typically, the asset size of ETFs doubles roughly every five years, but it took only 3.7 years to grow from $5 trillion to $10 trillion, according to analyst Eric Balchunas. He boldly predicts that ETF assets in the U.S. will reach $25 trillion in the next decade.

In addition to Wall Street in the U.S., similar trends are occurring elsewhere. According to ETFGI in the U.K., global net inflows of ETF assets have amounted to $1.45 trillion so far this year, reaching $14 trillion.

In contrast to the record size of ETFs, mutual fund assets are declining. Morningstar recently said its mutual funds had net outflows of $217 billion through August, while ETFs had inflows of billions of dollars.