Brian Legarth and Kenneth Hartzfeld
CPI is the weighted average of prices of a host of consumer goods, such as goods, services, transportation, and medical care. It is a general metric of the price that living costs. CPI is used in the calculation of changes in costs of living, and is an important teller of inflation and deflation.
The currency in circulation metric measures the total value of coins and cash bills that have ever been issued subtracted by that which the government has removed from circulation. Currency in circulation is a very small portion of the actual money being transferred in today's economy that is widely digital. Since the Great Recession of 2008, the Currency in Circulation has nearly doubled.
Both metrics are used to show inflation and deflation, but in terms of currency in circulation, the value has almost doubled over the last 10 years, while the CPI has only grown by about 20%. CPI seems to be the more accurate metric for inflation growth, as inflation hasn't doubled in the last 10 years.