In economics, inflation is a rise in the general level of prices of goods and services in an economy over a period of time. When the general price level rises, each unit of currency buys fewer goods and services; consequently, inflation is also a decline in the real value of money—a loss of purchasing power in the medium of exchange which is also the monetary unit of account in the economy. A chief measure of general price-level inflation is the general inflation rate, which is the percentage change in a general price index (normally the Consumer Price Index) over time.

Inflation can have adverse effects on an economy. For example, uncertainty about future inflation may discourage investment and saving. High inflation may lead to shortages of goods if consumers begin hoarding out of concern that prices will increase in the future.

Economists generally agree that high rates of inflation and hyperinflation are caused by an excessive growth of the money supply. Views on which factors determine low to moderate rates of inflation are more varied. Low or moderate inflation may be attributed to fluctuations in real demand for goods and services, or changes in available supplies such as during scarcities, as well as to growth in the money supply. However, the consensus view is that a long sustained period of inflation is caused by money supply growing faster than the rate of economic growth.

Today, most economists favor a low steady rate of inflation. Low (as opposed to zero or negative) inflation may reduce the severity of economic recessions by enabling the labor market to adjust more quickly in a downturn, and reduce the risk that a liquidity trap prevents monetary policy from stabilizing the economy. The task of keeping the rate of inflation low and stable is usually given to monetary authorities. Generally, these monetary authorities are the central banks that control the size of the money supply through the setting of interest rates, through open market operations, and through the setting of banking reserve requirements.

Origins

Inflation originally referred to the debasement of the currency. When gold was used as currency, gold coins could be collected by the government (e.g. the king or the ruler of the region), melted down, mixed with other metals such as silver, copper or lead, and reissued at the same nominal value. By diluting the gold with other metals, the government could increase the total number of coins issued without also needing to increase the amount of gold used to make them. When the cost of each coin is lowered in this way, the government profits from an increase in seigniorage. This practice would increase the money supply but at the same time lower the relative value of each coin. As the relative value of the coins decrease, consumers would need more coins to exchange for the same goods and services. These goods and services would experience a price increase as the value of each coin is reduced.