What causes the population explosion?.

             Figure 3 (a line graph showing world population growth) shows that the world population explosion began in about 1870 and has continued since then. The three broken lines show the three possible predictions for the world population in the future (the high, medium and low series'). The high assumes that birth rates and death rates will decline at a standard rate, the medium variant assumes rapid decline in both birth and death rates and the low variant assumes a rapid fall in birth rates but a standard decline in death rates.

             Changes in population are caused by birth and death rates. If the birth rate is higher than the death rate then there will be a population increase, if the death rate is higher than the birth rate then there will be a population decrease. The larger the difference between the birth and death rates are for a country, the larger the population increase or decrease is. .

             e.g.1. Yemen: birth rate = 46 death rate =11 natural increase =3.5% (1997) compared to.

             Denmark:birth rate =13 death rate =12 natural increase = 0.1% (1997).

             In both Yemen and Denmark the birth rate is higher than the death rate so the population will increase but the difference between the birth rate and death rate in Denmark is much smaller than the difference between the birth rate and death rate of Yemen so the natural increase in Denmark is lower so the population will not increase at such a rapid rate.

             e.g.2. Bulgaria: birth rate = 9 death rate =14 natural increase = -0.4% (1997).

             Germany: birth rate =10 death rate =11 natural increase = -0.1% (1997).

             In both Bulgaria and Germany the death rate is higher than the birth rate resulting in a negative population increase (population decrease) but the difference between the birth rate and death rate of Bulgaria is higher than the difference between the birth rate and death rate of Germany so Bulgaria's population increase is higher than Germany's population decrease.