The optimum population of a country is reached when the

The optimum population of a country is reached when the output per head is at its highest with a given volume of resources. This means that the country has reached a point where its population is neither too large nor too small for the available resources to support. At this point, every individual in the population is able to produce and consume at the highest level possible, without putting too much strain on the available resources. Any increase or decrease in population from this point will lead to a decrease in output per head, which will ultimately lead to a decrease in the standard of living.