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.
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.