Index directory
Indices measure a market rather than a company: they cannot be bought directly, and their level reflects the weighted movement of their constituents. These pages show the live level, the range, and how the index is built.
10 pages
All pages
What an index level actually represents
An index is a calculated number, not a tradable security. Its level reflects the weighted movement of its constituents against a base value set at launch, so the number itself has no unit of currency in any meaningful sense. Exposure to an index is taken indirectly, through index funds, ETFs or derivatives, each of which carries its own costs and risks.
How construction changes behaviour
Most widely followed indices are weighted by free-float market capitalisation, meaning the largest companies by tradable value dominate the level. That concentration is why an index can rise while most of its constituents fall. Some indices are weighted by price instead, which gives higher-priced shares more influence regardless of company size. Rebalancing dates, when constituents or weights change, concentrate passive fund trading.
Using index pages alongside stock pages
Comparing a stock against the index it belongs to separates market-wide movement from company-specific movement. If a stock falls two percent on a day its index fell two percent, very little of that move is about the company. This is the single most useful habit these pages support.