Why do some analysts give the impression that a declining birth rate means the population is declining?
We don’t know. A declining birth rate is not the same thing as a declining population. For example, the current total fertility rate in the UK is about 1.64 children per mother and it has been steadily declining. UK population, however, is continuing to increase (by more than 200,000 a year). One reason is the addition to population caused by an excess of immigration over emigration (net inward migration). Another is natural increase (the excess of births over deaths in a year). This natural increase results in part from changes in the size and/or age structure of the population, for example, a whole generation ago. The same applies to world population – the global birth rate is falling, but world population is still increasing by about 77 million a year and will continue to increase for a long time. A population can grow faster than it did a few years before even if its birthrate is falling – this is partly due to the ‘compound interest’ effect of births – just as 5 per cent interest
