That's exactly what I was referring to in my first post. Percentages really don't ever seem to be a percentage of the actual current value. Ore production percentage increases are a percent of total possible production. Trade value percent increases and decreases are not a percentage of the value you currently get, but are a percentage of the total base trade value (so a 10% percent increase is actually a 20% increase from your base share). I see no reason to assume combat modifiers are any more transparent. It's probably nowhere near as simple as the possible equations you've proposed above.