The following is an updated version of a post I wrote about a year ago to explain fairmath to someone else:

The complicated thing about Fairmath is understanding that **increases are based on how much you still have to gain**, while **decreases are based on how much you have to lose**.

So if you have say a starting strength score of 40%, then there is only 40% you can lose, but 60% you can still gain. Therefore a 50% loss from a score of 40% will be smaller than a 50% gain, because half of 40 is less than half of 60.

Mathematically:

40+(0.50*60) = 40+30 **(50% of what you didn’t have is gained)**= 70

40-(0.50*40) = 40-20 **(50% of what you had is lost)**= 20

The difference is even more dramatic if your score is very high or very low. Lets say you have a starting strength score of 90%, then you have have only 10% more that you can gain, but 90% that you can lose. So losing 50% or half of that 90% you already have would be far more than gaining 50% or half of the remaining 10% you don’t yet have.

Mathematically:

90+(0.50*10) = 90+5 **(50% of what you didn’t have is gained)**= 95

90-(0.50*90) = 90-45 **(50% of what you had is lost) **= 45