““Because we bump into reinforcing loops so often, it is handy to know this shortcut: The time it takes for an exponentially growing stock to double in size, the “doubling time,” equals approximately 70 divided by the growth rate (expressed as a percentage). Example: If you put $100 in the bank at 7% interest per year, you will double your money in 10 years (70 ÷ 7 = 10). If you get only 5% interest, your money will take 14 years to double.””
![“[P]opulation, when unchecked, goes on doubling itself every twenty-five years,…” quote by Thomas Malthus](https://sms4smile.com/quotes/img-quotes/16b/thomas-malthus-7621_circumstances_p-opulation-when-unchecked-goes-on-doubl_324443.jpg)
