Investors steered an estimated $17.1 billion into exchange-traded funds and notes in July, bringing their total investment in the products to $93 billion for the year, according to the latest data from the ETF Industry Association. The $93 billion represents a 31% increase from the $71.1 billion that ETFs and ETNs posted in inflows in the first seven months of 2011. 

U.S. equity-based ETFs and ETNs drew the largest share of July's $17.1 billion inflow, taking in $14.2 billion. Global equity ETFs, which posted almost $3 billion in inflows, gobbled most of the rest.

The most popular ETF in July was the SPDR S&P 500, which attracted an estimated $2.9 billion in inflows. Coming in a distant second and third were Vanguard's MSCI Emerging Markets ETF and the iBoxx High Yield Corp Bond ETF from iShares, which captured $1.5 billion and $968 million, respectively, in inflows for the month.

Assets in U.S.-listed ETFs and ETNs totaled approximately $1.21 trillion at the end of July, up 9% from $1.11 trillion a year ago. The bulk of the assets were held in equity- and REIT-based ETFs, which totaled $866 billion, according to the data.

The ETF Industry Association tallied a total of 1,486 products at the end of July, a 15% increase from the 1,295 products listed a year ago.