Inflation is an upward movement in the average level of prices. Its opposite is deflation, a downward movement in the average level of prices. The boundary between inflation and deflation is price stability.

The Link Between Inflation and Money

Because inflation is a rise in the general level of prices, it is intrinsically linked to money, as captured by the often heard refrain "Inflation is too many dollars chasing too few goods". To understand how this works, imagine a world that only has two commodities: Oranges picked from orange trees, and paper money printed by the government. In a year where there is a drought and oranges are scarce, we'd expect to see the price of oranges rise, as there will be quite a few shillings chasing very few oranges. Conversely, if there's a record crop or oranges, we'd expect to see the price of oranges fall, as orange sellers will need to reduce their prices in order to clear their inventory. These scenarios are inflation and deflation, respectively, though in the real world inflation and deflation are changes in the average price of all goods and services, not just one.

Inflation and the Money Supply

We can also have inflation and deflation by changing the amount of money in the system. If the government decides to print a lot of money, then dollars will become plentiful relative to oranges, just as in our drought situation. Thus inflation is caused by the amount of dollars rising relative to the amount of oranges (goods and services), and deflation is caused by the amount of dollars falling relative to the amount of oranges. Thus, inflation is caused by a combination of four factors:

• The supply of money goes up.
• The supply of other goods goes down.
• Demand for money goes down.
• Demand for other goods goes up.