NYSE Amex Composite Index

See: New York Stock Exchange.

The “NYSE Amex Composite Index” is a big name for an index focused on small companies. This market capitalization-weighted index has gone by a couple of other names in the past—Amex Composite Index and New York Stock Exchange Alternext U.S., specifically—but no matter what we call it, its premise is the same: it gives us a picture of how small business stocks are doing. That’s because most of the 200+ securities included in the index are micro-cap, small-cap, and nano-cap stocks, and how they perform tends to be pretty representative of smaller-cap stocks in general.

Anyway, generally speaking, this index does well when investors are feeling daring and confident. When they’re not, they tend to shy away from investing in smaller companies, and stick with the often safer and more predictable larger-cap stocks.