Mortality pattern affects population growth rates because a high mortality rate will offset the population-growth effects of a high birthrate. It is important to remember that mortality patterns often disproportionately affect different groups. If the mortality rate were atypically high among fertile-age women, this would have an even more powerful impact on population growth.
Age distribution is also important to growth rate because it describes what percentage of the population is at a child producing age. An age distribution that is weighed toward elder people can expect a lower future growth rate than a young-slanted age distribution, since a larger portion of the young population will likely have babies in the future.
