A measure of how fast a currency loses its value. That is, the inflation rate measures how fast prices for goods and services rise over time, or how much less one unit of currency buys now compared to one unit of currency at a given time in the past. The inflation rate may increase due to massive printing of money, which increases supply in the economy and thus reduces demand. Equally, it may occur because certain important commodities become rarer and thus more expensive. Central banks attempt to control the inflation rate by increasing and decreasing the money supply. The inflation rate is important to fixed-income securities, as the returns on these securities may not keep up with inflation, and thus result in a net loss for the investor.