IUSG is one of the more well-known funds in the US growth space. IUSG's index is a subset of the S&P 900 that uses a screening process based on only three factors, such as sales growth, changes on earnings-to-price ratio, and momentum, to identify firms with growth characteristics. The index is market cap-weighted and rebalanced every quarter. Prior to January 23, 2017, the fund traded as iShares Core Russell U.S. Growth ETF and tracked the Russell 3000 Growth Index.