Although advertisements and news stories about the latest product developments in exchange-traded funds are rife, there is no data available that allows investors to track the funds, according to mutual fund analysts and executives. That is because fund data and rating services are struggling to determine an accurate method of tracking the funds, they said.

Part of the challenge is that exchange-traded funds are continuing to change rapidly, said Edward Rosenbaum, director of research for Lipper of Summit, N.J. Currently, Lipper tracks and classifies only WEBs - that track international exchanges - but the firm is working on how to follow other types of exchange-traded funds, he said.

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