A negative percent increase is the same as percent decrease. For example, in aerobic
cellular respiration 686 kcal in one mole of glucose in transferred into 304 kcal in 38
moles of ATP. If you plug 686 and 304 into the above calculator boxes and click on
solve, the result is -55.68513119533528% which rounds off to -56 percent. In other
words, the energy decrease (dissipated) is 56 percent and the efficiency is 44 percent.
$80 reduced to $40 is a decrease of 50%, but $40 raised to $80 is an increase of 100%