I realized that the laws governing how a virus spreads are the same as those that govern how a product of a startup spreads. The similarity struck me while reading a book about the Coronavirus. The book is called Apollo's Arrow and is written by Nicholas Christakis. In his book he explains how the spread of a Virus is measured with the so called reproduction number R.
R measures how strongly a Virus is spreading. It shows how infectious it is in the absence of any measures. If one person transmits the disease to ten others, then we say that the Virus has a reproduction number of 10 or R 10.
As a startup founder you can apply this way of measurement to two things: - How many users recommend my product to others (spread the infection) - How many of the new users actually keep using your product (are infected) If I am not mistaken, R is so important for your startup that it should be translated into your specific growth equation.