Index

An index is a rules-based statistical measure that tracks the performance of a defined group of instruments, markets, or economic observations.

Index methodology determines eligibility, weighting, rebalancing, corporate-action treatment, and calculation, so two indices covering similar markets can behave differently. An index itself is generally a measure rather than an investable account asset; funds and derivatives seek to provide related exposure and introduce their own costs and tracking differences. Past index performance excludes some practical constraints and does not predict future returns.