There are many ways for fund managers to track the performance of an index. These ‘replication methods’ fall into two broad categories, physical and synthetic. Physical ETFs own the underlying stocks or bonds that comprise the benchmark index; whereas a synthetic ETF aims to deliver the index performance through a swap provided by an investment bank. A swap is a type of derivative contract where two parties agree to exchange (“swap”) one stream of flows for another. At Invesco, we pioneered a synthetic method called “physical with swap overlay” whereby the ETF holds a basket of quality securities, which are not the same as those in the index but are expected to produce most of the returns. To reduce tracking error, the ETF has swaps often with multiple counterparties (investment banks) that pay the difference between the index return and the return of the basket of securities.