# Rule of 70

… a core concept in Macroeconomic Policy

Click for MRU video

### Concept description

The rule of 70 says the doubling time is 70/growth rate and is a useful rule of thumb for quickly calculating the doubling time for something (e.g. population, GDP, internet nodes) that is growing at a constant rate.

Alex Tabarrok (reference below) has a 5-minute MRU video (on right) that uses The Rule of 70 to compare the implications of differing growth rates in GDP and population.

The logarithmic scales are explained in more detail at the Khan Academy at https://www.khanacademy.org/math/algebra2/exponential-and-logarithmic-functions/logarithmic-scale/v/logarithmic-scale, accessed 22 April 2016.

###### MRU practice questions

See http://www.mruniversity.com/rule-70-practice-question, accessed 22 April 2016.

1. If a process is growing at a rate of x percent per period, then the doubling time is approximately 70/x periods. This is known as:
1. th
###### Source

Alex Tabarrok, Rule of 70, Marginal Revolution University, at http://www.mruniversity.com/courses/development-economics/rule-70, accessed 22 April 2016.

Atlas topic and subject

Wealth of Nations and Economic Growth (core topic) in Macroeconomic Policy.