(Bloomberg News) Exchange-traded funds in January attracted the most money in 16 months, driven by record deposits to bond ETFs.

Investors poured $34.1 billion into ETFs worldwide, the most since September 2010, according to data compiled by New York-based BlackRock Inc., the industry's largest provider. Fixed-income ETFs gathered $9.1 billion, compared with the previous high of $6.7 billion in January 2009.

The popularity of low-cost index-based strategies surged among bond investors in the past year as yields hovered near record lows and some top long-term performers, including Bill Gross at Pacific Investment Management Co., trailed markets. Assets in bond ETFs, including exchange-traded notes and trusts, have more than quadrupled since the beginning of 2008 to $271 billion, BlackRock data show.

"We are reaching a critical mass with fixed-income ETFs," Matt Tucker, head of fixed-income strategy at BlackRock's ETF unit iShares, said in a telephone interview. "We're seeing investors exercise more control of their investing through ETFs."

U.S.-registered funds accounted for $7.2 billion of bond ETF deposits in January, he said. Of that, two-thirds went into funds focused on investment-grade and high-yield corporate bonds.

Bond ETF investors are concentrating less on the broadest indexes, Tucker said. Funds that track the BarCap U.S. Aggregate Bond Index captured 6 percent of the money that flowed into all U.S. bond ETFs in January, he said. The same funds manage 20 percent of U.S. bond ETF assets.

"Investors are shifting to more customized segments in the market," Tucker said.

ETFs, which typically hold baskets of securities that track an industry or market benchmark, trade throughout the day like stocks.

In September 2010, the funds attracted $39.1 billion, according to BlackRock.