NEW YORK ( TheStreet) -- State Street's SPDR S&P 500 ETF ( SPY) -- the oldest, largest ETF in the U.S. -- is hemorrhaging cash in a trend that may continue no matter which way the market's headed. The iconic SPY, which is designed to track the S&P 500 index, saw net outflows of more than $19.4 billion in 2009 and $16 billion in January 2010 alone. According to State Street's Web site, the fund's total assets were $66.074 billion as of Feb. 4. SPY's assets as of Dec. 31, 2008, and Dec. 31, 2009, were $84.9 billion and $93.9 billion respectively. Some of SPY's outflows can be traced to a broader retreat from U.S. equities. Other iconic broad-market ETFs also had recent asset outflows. The PowerShares QQQ ( QQQQ) and Diamonds Trust ( DIA) had net outflows of $1.2 billion and $705 million in January 2010, respectively. To just compare SPY's losses to those of other older, entrenched, broad-market ETFs, however, is to miss the most important shift. The ETF industry is evolving as it expands, and the customer is changing as well. ETF investors have learned to drive a hard bargain, and the "old guard" of ETF symbols is making way for the new. As investors have become increasingly educated about ETFs, they have begun to notice three key distinguishing factors: fees, strategy and availability. The greatest evidence of this change has been the relative strength, and even growth, of the iShares S&P 500 ( IVV), Vanguard MSCI Total Market ( VTI) and Schwab S Broad Market ( SCHB) ETFs over the past year.