The Invesco Dorsey Wright Basic Materials Momentum ETF (PYZ) seeks to replicate the performance of the Dorsey Wright Basic Materials Technical Leaders Index. This fund typically allocates a minimum of 90% of its total assets to the securities that comprise its benchmark index. The underlying index is structured to identify companies exhibiting strong relative performance, or momentum, and is composed of at least 30 securities chosen from the NASDAQ US Benchmark Index. Relative strength defines how a security's performance within a given market segment compares to its peers over a period of time. Both the ETF and its guiding index undergo adjustments and re-composition every three months.