SPTM is a part of the SPDR Portfolio ETF line up, a collection of core-exposure funds that track S&P indexes. The fund tracks the S&P Composite 1500 Index. The S&P's index committee chooses at least 1,500 securities to represent the US equities market, not necessarily the 1,500 largest by market cap, which can lead to some omissions of single names. SPTM securities are added and removed on an as-needed basis and are rebalanced on a quarterly basis. There is no scheduled reconstitution. Rather, changes in response to corporate actions and market developments can be made at any time. The fund may also invest on futures contracts. Prior to January 24, 2020 the fund tracked the SSGA Total Stock Market Index.
