If you look at how the population structure of countries like the U.K. change it is possible to identify four stages

1. High birth rate and high death rate, low natural increase - the population grows slowly
2. High birth rate and decreasing death rate, large natural increase - rapid growth in population
3. Both birth and death rates are falling, still large natural increase - population still growing, but at a slower rate
4. Low birth and death rate, low natural increase, slow population growth