Average Annual Rate of Growth and Rounding of Data
April 12, 2021
In some statistical tables in Woods & Poole publications, data are presented for the average annual rate of growth for a particular variable over a specified time period. The average annual rate of growth is the compounded growth of a variable over time. Thus, a 3.0% average annual rate of growth between 1970 and 1980 for population would mean that, on average, the population increased 3.0% each year between 1970 and 1980. An average annual rate of growth can be calculated by dividing the data year t+n by data year t and calculating the nth root of the quotient (where n is the number of years between t and t+n). Subtract one and multiply by 100 to convert the growth into percent. A negative average annual rate of growth would mean a decline in the variable over time.
For some variables, data are rounded in the Woods & Poole database. Data for the U.S., states, Core Based Statistical Areas (CBSAs), and other regions are the sum of counties. Due to rounding, the subtotals in Woods & Poole data tables may not exactly equal the components. Special calculations in some data tables (e.g., population growth rates) also may not exactly equal the data because of rounding. Since the U.S. and state data are based on county estimates, they may differ from U.S. and state data available from other sources.