As long ago as in the 1990s it was possible to make forecasts, particularly regarding the spread of HIV, suggesting that in certain cases up to 25% of the adult population in some countries would be infected.
Allerede i begyndelsen af 1990'erne var det muligt at opstille prognoser for især udbredelsen af hiv, som viste, at i visse tilfælde ville op til 25% af den voksne befolkning i visse lande blive inficeret.