In the Real Barenzia is it not stated that Dunmer parents usually only have one child? How can this be? Is the population of Morrowind cutting itself in half every generation? let’s say you have a population of 100 Dunmer. They form 50 pairs (sets of parents). After 1000 years or however long the lifespan is all the parents have died. If each pair only had one kid then there would now only be a population of 50 (1 kid per set of parents). And this is assuming everyone in the initial population A) found a match of the opposite gender B) Had kids with their match and C) that the child lived.
In reality, as long as there is a guarantee of death (lifespan is irrelevant) a population needs an average birthrate of 2.5 or so per set of parents just to maintain a static not growing population. The .5 is there to make up for people who don't have kids, die before procreating, or who's kids die before reaching adulthood.
How then can this statement be true? Are the Dunmer dying out? Do enough of them become immortal through vampirism or magic to offset this? As long as they are merely long-lived they still need to replace their own numbers with each generation to maintain their population, and that means 2 or more per household.
It dosen't say that thou. It says that it is just common for them not to have more than one child not that they usually only have one child. They often have one child but most of time they have two and the limit is said to be four.