Growth proponents may claim that "small" (such as 1% per year) increases in growth will not lead to noticeable changes in a community. The doubling time formula is a great tool for rebutting this argument. The formula calculates the number of years that it will take a population to double in size, given a certain growth rate per year. The exact formula is
| n = | ln 2 |
| --------------- | |
| ln[1 + (r/100)] |
where n is the doubling time (in years) and r is the growth rate (in percent per year).
For instance, when r is 1 (one percent growth per year), n equals 69.7 (the approximate life span of an American). So if your community's population were to grow by 1% per year, the number of people around you would double during your lifetime.
The formula can be approximated by the equation: n = 70/r
A fascinating lecture by Dr. Al Bartlett on the doubling formula and the incredible ramifications of continued growth is available on the Global Public Media website.