Overall Preston found that improvements in health technology (the upwards shifts in the curve) accounted for 75% to 90% of the increase in life expectancy, while income growth (movement along the curve) was responsible for the rest.
Preston leidis üldjoontes, et paranenud tervisehoiu tehnoloogia (liigutab graafikut ülespoole) annab 75–90% eluea kasvust, samas kui sissetuleku kasv (liikumine pikki kõverat) on ülejäänud kasvuosaks.