Discovery desk
S&P 500 heat map
Every member of the index, sized by market value and coloured by how it has done this year — so you can see whether the year’s move is broad, or a few of the largest companies carrying it.
How to read it
Box area is market value, the way the index itself is weighted, so the largest companies take the most room — and the most say in the index’s return. Colour is each member’s price return since the last close of last year, before dividends.
Breadth is how many take part. When the cap-weighted return runs well ahead of the equal-weight one and the median, the index is being carried by its largest members; when they are close, the move is broad. The share of members above their 200-day average is the slower read of the same question, the 50-day the faster one.
A company with two classes of shares in the index — Alphabet’s GOOGL and GOOG, Fox, News Corp — is one box, priced by its first-listed class and counted once, so it is drawn at its real size rather than twice it.
A member that began trading this year — a spin-off or a new listing — is measured from its first close, and says so when you point at it.
Research, not a recommendation. The member list is kept by Wikipedia’s editors rather than taken from S&P Dow Jones Indices, so a change in membership can show a day late, and the cap-weighted figures weight every share rather than the float the index uses, so they land near the index’s own return without matching it.