How to Calculate Annual Growth
- 1). Divide the population at the later time by the corresponding population at the earlier time. For example, if the population is 50,000 in the 2003 and 100,000 exactly four years later in 2007, then divide 100,000 by 50,000, giving you an answer of 2. Denote this multiple by the letter M.
- 2). Compute the reciprocal of the number of years between the two population measurements, and denote that number by the letter T. In the example, T = 4 because the two measurements are four years apart. Compute 1/T = 1/4 = 0.25. For a more complex example, use your calculator to divide 1 by the number of years, or enter the number in your scientific calculator and press the "1/x" key.
- 3). Raise M to the power 1/T. In the example, you raise 2 to the power 0.25. Use a scientific calculator to compute X to the power Y. Using the Online Scientific Calculator, you enter "2", press the "X to the Y" key on the top row, enter ".25", and press the "=" key, which gives you an answer of 1.189. You may have to use a different key sequence on your calculator.
- 4). Subtract 1 from the answer in Step 4. In the example, 1.189 -- 1 = 0.189. This is the annual growth rate expressed as a decimal. Multiply by 100 to express the rate as a percentage, which in this case would be 18.9%.
