Page 119 - Florence County, SC Florence County 2032: Connecting Our Past, Defining Our Future

survival method of forecasting. For each county, same amount is being added to an ever-expanding
each five-year age-gender cohort’s population base (in the case of Pottawatomie County, adding
change was forecasted in five-year increments, 3,395 residents per decade). Exponential growth
starting with U.S. Census Population Estimates data projections produce higher numbers than linear
for 2014. Under this forecasting method, each cohort by assuming a constant rate of growth over time.
group’s population is forecasted forward five years at This is similar to the power of compound growth
a time by using the estimated mortality rate and the in a savings account over time; the interest (i.e.,
estimated migration rate for that age-gender cohort growth) rate may not change, but it is being applied
in the county to projection population changes for to an ever-expanding balance, resulting in larger
that age-gender cohort.” (CEDBR, February 2016 and larger interest earnings over time. In the case
release). of Pottawatomie County, the Exponential and Linear
Growth scenarios result in a population difference of
Projections Based on Varying Quantities 4,292 because the growth increments are large.
and Rates of Growth
The Exponential Growth line is based on the 1.7
Another population projection method extends percent compound annual growth rate (CAGR)
historical trends to future years. Linear growth the County experienced from 2010 to 2016. The
forecasts are “straight line” projections that result Exponential Growth line leads to a 2040 population
in the same absolute number of new persons of 36,081 while the Linear Growth line, labeled as
being added to the population in each period. This “Steady Numeric Growth” on the chart, leads to a
produces a declining rate of growth over time as the 2040 population of 31,789.

Figure 4, Pottawatomie Projections based on Varying Quantities and Rates of Growth

40,000
36,081
35,000 33,860
31,789
30,000
23,661
25,000

20,000

15,000

10,000
1970 1980 1990 2000 2010 2016 2020 2025 2030 2035 2040
Historical Data 11,755 14,782 16,128 18,209 21,604 23,661
Wichita State, CEDBR 23,661 24,772 26,770 28,929 31,298 33,860
Steady Numeric Growth 23,661 24,999 26,642 28,394 30,044 31,789
Exponential Growth 23,661 25,632 27,919 30,411 33,125 36,081

112 | Plan Pottawatomie County 2040 Adopted - August 19, 2019