I'm trying to compare ETFs using etfdb. I saw two ETFs that track identical indexes, but both have very different returns after 5 years: [IVW][1] 5-year return was 125.43%, with an expense ratio of 0.18%. [RPG][2] 5-year return was 183.31%, with an expense ratio of 0.35%. Both of these ETFs track the S&P 500/Citigroup Pure Growth Index. I was under the impression that ETFs were passively managed, and therefor two ETFs tracking the same index would have the same return, less expense ratios. Is that an incorrect assumption--are (some) ETFs actively managed? Is there something else that I'm not accounting for which would justify different returns for ETFS tracking identical indices? [1]: http://etfdb.com/etf/IVW/#fundamentals [2]: http://etfdb.com/etf/IVW/#fundamentals