Best Guesses
A Sampling of Forecasts for World Population in 2000 
In 1695, one demographer predicted global population would reach about 500 million by the year 2000. Although forecasts have gotten more accurate over time, predicting population remains tricky due to complicated variables ranging from consumption rates to technological innovation.
Source: Caselli G., J. Vallin, and G. Wunsch (eds.). 2006. Demography: Analysis and Synthesis, volumes 1–4: A Treatise in Population. Academic Press, Burlington, Massachusetts.
