The fund invests in financial instruments that ProShare Advisors believes, in combination, should produce daily returns consistent with the fund's investment objective. The index is a measure of large-cap U.S. stock market performance. It is a float-adjusted, market capitalization-weighted index of 500 U.S. operating companies and real estate investment trusts selected through a process that factors in criteria such as liquidity, price, market capitalization, financial viability and public float. The fund is non-diversified.