NEW YORK (TheStreet) -- The National Stock Exchange's new report on ETF flow data for May provides a wealth of information on investor preferences.

Overall, May was a trying month for investors. As the global marketplace ran into turmoil, investor interest in exchange-traded funds waned. For the first time in 2011, the industry saw net outflows. The $777 million in net outflows marked a dramatic shift from April, when there were $20 billion in inflows.

Industry leaders including

State Street

(SST)

, PowerShares, and

BlackRock

(BLK) - Get BlackRock, Inc. Report

witnessed the most staggering outflows, totaling $5.98 billion, $2.16 billion and $1.95 billion respectively. Smaller fund providers such as ETF Securities and Guggenheim ran into notable headwinds as well.

Much of these ETF goliaths' outflows can be attributed to general investor disinterest in veteran broad index-based ETFs.

SPDR S&P 500 ETF

(SPY) - Get SPDR S&P 500 ETF Trust Report

,

PowerShares QQQ

(QQQ) - Get Invesco QQQ Trust Report

, and

iShares Russell 2000 Index Fund

(IWM) - Get iShares Russell 2000 ETF Report

led the industry with outflows in May, with $4.91 billion, $2.54 billion, and $2.06 turning to the exits respectively.

Many of the largest physically-based precious metal ETFs were shunned as well. As volatility perked across the commodities spectrum, investors fled funds such as

iShares Silver Trust

(SLV) - Get iShares Silver Trust Report

and

SPDR Gold Trust

(GLD) - Get SPDR Gold Trust Report

.

Interestingly, there was one physically-based fund from the precious metals realm that proved popular in May. The

iShares Gold Trust

(IAU) - Get iShares Gold Trust Report

ended the month with net inflows totaling $165 million. As in recent months, investor preference for IAU over GLD can likely be traced to the iShares product's reduced expense ratio.

Although the industry as a whole witnessed net outflows during May, it is important to note that not all fund providers closed out the month in the red. On the contrary, Vanguard and Van Eck managed to buck the trend, gathering up $7.05 billion and $985 million respectively.

Much of Van Eck's gains in May can be traced to a single fund, the

Market Vectors Agribusiness ETF

(MOO) - Get VanEck Vectors Agribusiness ETF Report

. During the month, this fund topped the list of inflow recipients, gathering nearly $1.50 billion as investors clamored for agriculture-related equities. Interestingly, the same could not be said for futures-based agriculture ETFs. The

PowerShares DB Agriculture ETF

(DBA) - Get Invesco DB Agriculture Fund Report

ended the month with $374 million in outflows, placing it among the 10 largest decliners.

Vanguard funds dominated the ranks of major inflow recipients, accounting for five of the top 10 positions. Among the products that saw the most popularity were the

Vanguard MSCI MidCap ETF

(VO) - Get Vanguard Mid-Cap ETF Report

,

Vanguard MSCI Small Cap ETF

(VB) - Get Vanguard Small-Cap ETF Report

,

TheStreet Recommends

Vanguard MSCI Small Cap Growth ETF

(VBK) - Get Vanguard Small-Cap Growth ETF Report

, and

Vanguard MSCI Emerging Market ETF

(VWO) - Get Vanguard FTSE Emerging Markets ETF Report

.

Many of the industry's biggest asset gainers were defense-focused, including the

Consumer Staples Select Sector SPDR

(XLP) - Get Consumer Staples Select Sector SPDR Fund Report

,

Healthcare Select Sector SPDR

(XLV) - Get Health Care Select Sector SPDR Fund Report

,

iShares Barclays 20+ Year Treasury Index Fund

(TLT) - Get iShares 20+ Year Treasury Bond ETF Report

and

PowerShares DB U.S. Dollar Index Bullish

(UUP) - Get Invesco DB US Dollar Index Bullish Fund Report

saw heavy inflows as investors sought protection from the market's volatility.

Meanwhile, more aggressive asset classes were avoided. The

SPDR S&P Metals & Mining ETF

(XME) - Get SPDR S&P Metals & Mining ETF Report

,

Energy Select Sector SPDR

(XLE) - Get Energy Select Sector SPDR Fund Report

and

SPDR KBW Bank ETF

(KBE) - Get SPDR S&P Bank ETF Report

saw heavy outflows.

The same could be said for commodity-related international funds.

Market Vectors Russia ETF

(RSX) - Get VanEck Vectors Russia ETF Report

and

iShares MSCI Canada Index Fund

(EWC) - Get iShares MSCI Canada ETF Report

saw $496 million and $321 million exit. China proved unpopular as well: the

iShares FTSE China 25 Index Fund

(FXI) - Get iShares China Large-Cap ETF Report

saw $679 million in outflows.

May's ETF flow data properly reflected the cautious and jittery market atmosphere that embodied this trying month. In the event that the market's soft spot persists as we close out the first half of 2011, many of the same themes that we witnessed during May will likely remain in play.

Written by Don Dion in Williamstown, Mass.

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At the time of publication, Dion Money Management owned PowerShares QQQ, iShares Gold Trust, iShares Barclays 20+ Year Treasury Index Fund, PowerShares DB U.S. Dollar Index Bullish and iShares MSCI Canada Index.