[a1369209993]

> Go up 50% then down 50% and you're not even, you're down 25%.

It helps if you measure in the right units[0], namely bits, orders of magnitude, or fractions thereof. Up 50% is log(1.5) = +0.58 bits, down 50% is log(0.5) = -1 bits, and indeed 0.58-1 = -0.42, or 1.5*0.5=0.75, down 25%.

0: Well, strictly speaking the problem is that up/down X% isn't even in units at all.

[economusty]

I assumed they meant dollars.