Subtract the country's population at the start of the year from the country's population at the end of the year to find the raw growth. For example, if the population of the country started at 100 million and increased to 102 million, subtract 100 million from 102 million to get a raw growth of 2 million.
Divide the raw growth by the initial amount to find the rate of growth. In this example, divide 2 million by 100 million to get 0.02.
Multiply the rate of growth by 100 to convert to percentage growth. Completing the example, multiply 0.02 by 100 to get 2 percent.