Which one of the Age Pyramid is ideal for a population and why?

If in an age pyramid the persons who are of pre reproductive age are large in number then that population is expanding because majority of population has reproducing power and age. A population having less number of children and more people who are about to cross their reproductive age shows a declining age pyramid. A population in which population of pre reproductive age is in proportion with reproductive population would show a stable or zero population growth, this is an ideal pyramid for a population as the population growth is stable and would not lead to either depletion of earthly resources or human resource.