Figure 1: Scenarios for future morbidity. The three major population scenarios in the upper part of the figure represent (1) depiction of a present health, (2) a future where both life expectancy and morbidity are both increased, and (3) a future where both the time period after first morbidity and the amount of morbidity are decreased, resulting in Compression of Morbidity. Shaded areas represent under the curve cumulative morbidity. In the Compression of Morbidity scenario, lifetime disability is decreased. National disability trends over time are the algebraic sum of the eight individual trajectories illustrated at the bottom of the figure and many more. Some individual scenarios may add morbidity to a population average and some may subtract from it. The area under the morbidity curve is a useful metric for population health or health-related quality-of-life. The variables that affect the area under the curve are many and complex and have not yet been well delineated (see text).