Reference #330: Thinking in Systems
The time taken for an exponentially growing stock to double in size (the "doubling time") is approximately 70 divided by the growth rate as a percentage. For example, if you put $100 into your bank returning 7% interest per year, you will double your money in 10 years. Note this doubling time is independent of the level of the stock.
Meadows. Thinking in Systems, 2008. (33)