Investors poured $12.84 billion into exchange-traded funds and notes during the month of June, bringing total half-year inflows to $75.91 billion, according to the latest statistics from the ETF Industry Association. That’s up 31% from the $57.94 billion ETFs and ETNs posted in inflows in the first half of 2011.

Fixed income-based ETFs and ETNs drew the largest share of the $12.84 billion inflow, taking in $4.82 billion in June. U.S. equity-based ETFs and ETNs, however, were not far behind with $4.60 billion in inflows.

June’s most popular ETF was PowerShares QQQ, which received an estimated $1.40 billion. The  iBoxx Inv Grade Corp Bond ETF from iShares and Vanguard’s MSCI Emerging Markets came in second and third, capturing $1.32 billion and $1.04 billion, respectively, in inflows for the month.

Assets in U.S.-listed ETFs and ETNs totaled $1.18 trillion at the end of June, up 7% from $1.11 trillion a year ago. The bulk of these assets were held in equity- and REIT-based ETFs, which totaled $839 billion, according to the data.

The ETF Association tallied a total of 1,476 U.S.-listed ETFs and ETNs at the end of June, a 15% increase from the 1,288 products listed a year ago.