What causes population to increase or decrease?

Demographers – population specialists – have concluded that the total population of the whole world will reach 7 billion on October 30, 2011 and will continue to increase thereafter.

There has been confusion about why the global population is increasing. What is causing an increase is not a rise in fertility but a fall in mortality. In other words, mortality is falling faster than fertility.

There is worry that if the global population continues to grow sooner or later the demand for goods and services will exceed their supply, causing all sorts of problems including famines and war over scarce resources. The relatively easy solution is to stop or reduce drastically population increase. This can be achieved in two ways – increase mortality and/or reduce fertility. Since it is morally wrong to recommend mortality increase, the only alternative is fertility reduction to 2.1 children per couple.

At continental, regional or national levels population increase or decrease is due to the difference between fertility and mortality (natural increase or decrease) and the difference between in-migrants and out-migrants (positive or negative migration). For example, when fertility exceeds mortality and in-migrants exceed out-migrants the population will increase. On the other hand when fertility is lower than mortality and in-migrants are fewer than out-migrants the population will decrease.