However, by looking at data pertinent to the world population numbers, we can get an idea of what drives their predictions. Projecting from now out to 2050 has difficulties because we don't know what changes are going to happen between now and then. See part III below for some links to relevant information.
Shaded area includes projected figures.
Note that some of these are merely slightly different ways of looking at the same phenomenon. Sometimes seeing the same thing from different angles helps give a better insight. However, contrast this with a rate of 5 in 1955. In all regions of the world, the fertility rate has been decreasing, often at an astonishing rate. This can account for the decline in the rate of increase in the world's population.