Plot 1
displays the observed age-specific death rates, along with the fitted force of mortality and a estimation of what it look like if there was no young adult mortality hump.
Plot 2
displays the age-specific contributions to the hump. These contributions are rescaled in order for the hump to sum up to 1.
Consequently, the surface can be interpreted as a probability density function (pdf), from which summary indicators can be computed such as the mean, mode and median age at death due to the hump.
Other summary indicators can be obtained by calling summary.morthump.