[kraghen]

I sometimes wonder if using logarithms would be more appropriate in most cases. Then we can simply add up the numbers as one "would expect".

We could choose the base to be ~2.7048138 such that 1% regular growth corresponds to 1% logarithmic growth. For low percentages they would mostly agree. But +40% would become +34% while -40% would become -51%, thus making the combined effect more apparent.