The population increase shown here is a measure how many more births there are than deaths. Changes to population sizes related to the movement of people are not shown. Every region of the world is experiencing overall natural increases in population size; just a few countries have natural decreases in population size.
The United Kingdom currently has more births than deaths occurring there. In recent years 645,000 people were born in the same year that 600,000 people died. Thus there was a net natural population growth of 45,000 in just one year. Part of the reason for this increase is due to improvements in health care that have resulted in longer life expectancies. Lengthening life expectancies (that is postponing deaths) has led to the current natural growth of the population of the United Kingdom – when these people do die the balance between the number of births and deaths will shift, almost certainly resulting in a natural population decline.