In May 2002, the TSX (Toronto Stock Exchange) 300 Index was converted to S&P/TSX Composite Index, increasing the flexibility of stock addition to, and deletion from, the Index. We study whether the increased flexibility enhances the Index’s ability to mimic the Canadian equity market performance and to represent the equity market. Our results show that the S&P/TSX Composite Index captures a higher proportion of the equity market and has a lower tracking error than the TSX 300 Index. This suggests that flexibility in updating the constituents of an index is an important determinant of the index’s ability to represent the underlying market.