Money Supply

The money supply is all the money available to spend in an economy. Economists measure it in rings, from the narrowest (physical cash) to broader ones like M2 that add bank deposits and savings. Central banks influence it through interest rates and asset purchases, and commercial banks expand it every time they make a loan.

The classic worry: if money grows much faster than the things it can buy, prices tend to rise. That link is the heart of the quantity theory of money, although in real life the relationship is messier and slower than the textbooks suggest.