Calculating Growth Rates

Population growth equation.

Planning Analysis: Calculating Growth Rates. 1. Calculating Percent (Straight-Line) Growth Rates. The percent change from one period to another is calculated from the formula: PR = Percent Rate V Present = Present or Future Value V Past = Past or Present Value. The annual percentage growth rate is simply the percent growth divided by N, the number of years.

In 1980, the population in Lane County was 250,000. This grew to 280,000 in 1990. What is the annual percentage growth rate for Lane County? VPresent = 280,000 VPast = 250,000 N = 10 Years. The population of Lane County grew 12 percent between 1980 and 1990 or at an rate of 1.2 percent annually. 2. Calculating Average Annual (Compound) Growth Rates. Another common method of calculating rates of change is the Average Annual or Compound Growth Rate (AAGR).

AAGR works the same way that a typical savings account works. Interest is compounded for some period (usually daily or monthly) at a given rate. Here's how it works: Let's say you had $100 dollars and invested it in an account that paid 5 percent annually. The table below shows how your interest accumulates.