In an article in the wall street journal, a professor of financial planning noted the effect of rising prices on purchasing power: "today, $2,000 a month seems reasonable [as an income for a retired person in addition to the person's social security payments], but 40 years from now that's going to be three cups of coffee and a donut."

The answer is: Inflation rate

Explanation:

Inflation rate measures the rate at which the average prices in an economy increases over time.

As the general level of prices rise in an economy, a unit of currency buys less than it did before. For example, 100 years ago you could buy a new car for less than $300.

wheres the chart? so i can answer.

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