Percentage point

A percentage point (pp) is the unit for the arithmetic difference of two percentages. For example, going from 40% to 44% is a 4 percentage point increase. In the literature, the percentage point unit is usually either written out, or abbreviated as pp, p.p. or %. Consider the following hypothetical example: In 1980, 40 percent of the population smoked, and in 1990 only 30 percent smoked. One can thus say that from 1980 to 1990, the prevalence of smoking decreased by 10 percentage points although smoking did not decrease by 10 percent (actually it decreased by 25 percent) – percentages indicate ratios, not differences.