In 2005, ETF assets passed the $300 billion mark. Today the Washington Post reports "of the $312 billion in ETFs at the end of 2005, Barclays managed 55 percent of it.

Barclays has an iShare for 102 indexes, including the S&P Small Cap 600, the Goldman Sachs Software Index and the MSCI Italy Index.

Merrill Lynch, State Street Global Advisors and Vanguard are other major investment firms that have issued ETFs in recent years.

But none has been as aggressive since 2004 as PowerShares. Of the 45 ETFs launched last year, 32 of them were issued by PowerShares. The firm’s specialty is finding value-added indexes."

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