# Unpredictable Movements of Velocity

What are Unpredictable Movements of Velocity in Money?

# What are Unpredictable Movements of Velocity in Money?

Velocity is a term that economists use to describe how quickly money circulates through the economy. We define the

velocity of money in a year as:

nominal GDP money supply

Specific measurements of velocity depend on the definition of the money supply used. Consider the velocity of M1, the total amount of currency in circulation and checking account balances. In 2009, for example, M1 was \$1.7 trillion and nominal GDP was \$14.3 trillion, so the velocity of M1 was 8.4 (\$14.3 trillion/\$1.7 trillion). A higher velocity of money means that the average dollar circulates more times in a year. A lower velocity means that the average dollar circulates fewer times in a year.

Changes in velocity can cause problems for monetary policy. To understand why, rewrite the definition of velocity so that the money supply is on the left-hand side of the equation. That is:

Money supply × velocity = Nominal GDP

Recall from The Macroeconomic Perspective that

Nominal GDP = Price Level (or GDP Deflator) × Real GDP.

Therefore,

Money Supply × velocity = Nominal GDP = Price Level × Real GDP.

We sometimes call this equation the basic quantity equation of money but, as you can see, it is just the definition of velocity written in a different form. This equation must hold true, by definition.

If velocity is constant over time, then a certain percentage rise in the money supply on the left-hand side of the basic quantity equation of money will inevitably lead to the same percentage rise in nominal GDP—although this change could happen through an increase in inflation, or an increase in real GDP, or some combination of the two. If velocity is changing over time but in a constant and predictable way, then changes in the money supply will continue to have a predictable effect on nominal GDP. If velocity changes unpredictably over time, however, then the effect of changes in the money supply on nominal GDP becomes unpredictable.

The reasons for these sharp changes in velocity remain a puzzle. Economists suspect that the changes in velocity are related to innovations in banking and finance which have changed how we are using money in making economic transactions: for example, the growth of electronic payments; a rise in personal borrowing and credit card usage; and accounts that make it easier for people to hold money in savings accounts, where it is counted as M2, right up to the moment that they want to write a check on the money and transfer it to M1. So far at least, it has proven difficult to draw clear links between these kinds of factors and the specific up-and-down fluctuations in M1. Given many changes in banking and the prevalence of electronic banking, economists now favor M2 as a measure of money rather than the narrower M1.

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