In trading on Thursday, shares of the iShares Dow Jones U.S. Basic Materials Sector Index Fund ETF (AMEX: IYM) crossed below their 200 day moving average of $68.25, changing hands as low as $68.12 per share. iShares Dow Jones U.S. Basic Materials Sector Index Fund shares are currently trading up about 0.3% on the day. The chart below shows the one year performance of IYM shares, versus its 200 day moving average: