Yes. Total species populations grow exponentially, and all of the growth is at the lowest age bracket. The number of living members in each birth cohort also

Yes. Total species populations grow exponentially, and all of the growth is at the lowest age bracket. The number of living members in each birth cohort also decreases exponentially as the cohort ages. It follows straightforwardly from this that population numbers by cohort will be on some log scale. We can naively estimate the relative size of these cohorts like this: >>> math.log(6) - math.log(1) 1.791759469228055 >>> math.log(121) - math.log(65) 0.6214032757011045 So we should expect a little under a 3x difference in favor of 0-5, which is in the rough ballpark of the 2.6x difference that the chart shows for 1950. Note that actual scientists work on this, and use much better methods than this (with confidence intervals and all that jazz). However, this method is a decent "try it at home" approximation, and still much better than comparing the number of years in the age cohorts.