Is half the world's population really below 'replacement-rate'?

A perennial activity of demographers is to estimate the percentage of the world's population which is above or below the 'replacement rate of fertility' [RRF]. However, most attempts to do so have been based upon, at best, oversimplified, or at worst, simply incorrect assumptions about what RRF actually is. The objective of this paper is to calculate the proportion of the world's population living in countries with observed period total fertility rates [TFR] below the respective calculated RRF, rather than the commonly used measure of 2.1. While the differences between comparing TFR to 2.1 or RRF are relatively modest in many periods when considering populations at the national level, a significant difference can be observed in the near future based upon India's fertility and mortality trajectories. Our exercise represents a means of 'correcting the record' using the most up-to-date evidence and using the correct protocol.