Percent Changes in Percentages

A Platonic percent change is the change in a logarithm. When the thing changing is measured in percent, that means the percent change is NOT the number of percentage points different. For example, the percent change in the saving rate is about 10% when it goes from 20% to 22%, just as the percent change in anything else that goes from 20 to 22 is about 10%. And if the saving rate went from 20% to 40%, by the Rule of 70, that would be a 70% Platonic percent change like any other doubling. To avoid confusion, you might want to convert the FROM and TO measured in percentage points to regular numbers by using the fact that the percent sign is just another way of saying one-hundredth. For example, 20% is point 2 and 40% is point 4. If you do this, you will avoid confusion when you do percent changes of things measured in percentages.