SPMD offers exposure to the mid-cap segment of the US equity market by tracking the S&P mid-cap 400 Index. Stocks are market cap-weighted and selected by the S&P Committee, with a consideration on sector balance by comparing the weight of each GICS (Global Industry Classification Standard) sector in the underlying index to its weight in the relevant market capitalization range of the S&P Total Market Index. SPMD has undergone several changes over the years previously trading under a different name, index, and ticker (RSCO) in November 2005 and once again in August 2016 (ticker: SMD). Finally, it also traded as the SPDR Portfolio Mid Cap ETF tracking the S&P 1000 Index until January 24, 2020. The fund employs a sampling strategy and its index is rebalanced on a quarterly basis.
