SPX's Correlation with M2 since 1980.

Definition
Correlation Coefficient (CC) is used in statistics
to measure the correlation between two sets of
data. In the trading world, the data sets would
be stocks, etf's or any other financial
instrument. The correlation between two
financial instruments, simply put, is the degree
in which they are related. Correlation is based
on a scale of 1 to -1. The closer the Correlation
Coefficient is to 1, the higher their positive
correlation. The instruments will move up and
down together. The higher the Correlation
efficient is to -1, the more they move in
opposite directions. A value at 0 indicates that
there is no correlation.
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M2 is a measure of the money supply that includes
cash, checking deposits, and easily convertible
near money.

M2 is a broader measure of the money supply
than M1, which just includes cash and checking
deposits.

M2 is closely watched as an indicator of money
supply and future inflation, and as a target of
central bank monetary policy.
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