Exchange-traded funds and exchange-traded notes enjoyed $17 billion in net investor inflows in May, according to new data released from the National Stock Exchange. That brings total net inflows for U.S.-listed ETFs in 2009 to $30 billion.

Industry assets rose from $540 billion to $594 billion, as the inflows were complemented by rising markets. The split is $588 billion for ETFs, and $6 billion for ETNs.

Inflows By Asset Class: Long-Only ETFs

Inflows were seen in all major asset classes in May, led by long international equity ETFs with $7.7 billion in net inflows.

Year-to-date, commodity and fixed-income ETFs lead the flows tables, with $18.7 billion and $17.9 billion in inflows, respectively. U.S. equity ETFs have actually suffered $35 billion in new outflows so far this year.

Inflows By Asset Class: Leveraged/Inverse ETFs

Leveraged and inverse ETFs allow investors to make aggressive bets on the direction of the markets, and watching flows into these funds gives a good window on how investors are positioning themselves for the short term.

In May, fund flows into leveraged and inverse ETFs were decidedly bearish, with traders pulling $900 million out of leveraged long ETFs and investing $395 million into inverse and inverse-leveraged ETFs. YTD, the flows are nearly balanced, with $2.5 billion in leveraged long inflows and $2.4 billion in inflows for inverse ETFs.

Looking by asset class, the numbers for May are stark. Investors poured $3.5 billion into inverse U.S. equity ETFs, while pulling $766 million out of leveraged long U.S. equity funds. Traders also soured on commodities in May, pulling money out of leveraged long commodity ETFs and putting some to work in inverse commodity funds.

Top Ten ETF Fund Flows: May 2009

The iShares MSCI Brazil ETF (NYSE Arca: EWZ) saw the largest net inflows of any ETF in May, with $1.5 billion in new money flowing into the high-performing fund. That was followed by the iShares MSCI Emerging Markets ETF (NYSE Arca: EEM) at $1.1 billion, and the Direxion Financials Bear 3x ETF (NYSE Arca: FAZ) and iShares FTSE/Xinhua China 25 (NYSE Arca: FXI), both at $1 billion.

Other top-ten-inflow ETFs worthy of note are the iShares Barclays TIPS ETF (NYSE Arca: TIP), which brought in $905 million and is now the seventh-largest ETF in the world; and the US Natural Gas ETF (NYSE Arca: UNG), which brought in $812 million and has attracted $1.7 billion YTD. Someone, clearly, is betting on a recovery in natural gas.

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