A diferença entre o número de nascimentos e o número de mortes corresponde a (as) :

The difference between the fertility rate and the death rate corresponds with the birth rate. When you take the number of children that have been born (alive) in a given year, and then minus the number of the people that have died in the same year, you get the birthrate. It can be positive, when there's more born children than people that died, or negative, when there's more people that died than born children.