Population growth rate (PGR) is the increase in a country's population during a period of time, usually one year, expressed as a percentage of the population at the start of that period. It reflects the number of births and deaths during the period and the number of people moving to and from a country. Countries with the most rapid population growth rates tend to be located in Africa and the Middle East. Countries with the slowest population growth rates tend to be located in Europe and North America.