A unit of proportion, equal to 0.01 or 1%. This unit is used commonly to describe changes in rates or other quantities that are stated as percentages. For example, an interest rate that rises from 8% to 10% is said to rise by two percentage points. Notice that if the changing rates are percentages of a quantity "y" then the percentage points are also percentages of "y". This is different from looking at the proportional change in the rates themselves: in our example, an increase from 8% to 10% is an increase of one-fourth (25%) in the actual interest rate. It often happens that a change of a few percentage points has a dramatic effect on the rate in question