ISTB covers a broad spectrum of short-dated, USD-denominated fixed-income instruments that includes US Treasurys, government-related issues (US and non-US), MBS, CMBS, ABS, Eurodollar bonds and investment-grade and high-yield corporate bonds. The fund uses a sampling indexing methodology thus, it may not hold all of the securities in the index. The market-value-weighted Index excludes municipal securities, coupon issues that have been stripped from bonds, structured notes, and private placements (excluding Rule 144A Bonds). The index undergoes monthly rebalance. Prior to September 3, 2014 the fund tracked the Barclays U.S. Government/Credit 1-5 Year Index.