Compound Annual Growth Rate (CAGR)
Interest rate at which a given present value would "grow" to a given future value in a given amount of time.
The formula is
CAGR = (FV/PV)^{1/n}  1
where FV is the future value, PV is the present value, and n is the number of years.
See the interactive graph for an explanation of the formula and some examples,
or the CAGR calculator.
Also see the CAGR of the S&P 500.
