I'm trying to get actual per-hour unit values ( not percentages ) on the resources upgrades so that I can compare the costs of the various upgrading options to their actual effect on production. What number are the upgrade percentages based on specifically, e.g. for a level 21 rum cellar, what is the base number the extra 10% is based on?
Not sure how much this helps but the starting value of rum production without any rum distilleries is 400.
Like Icy, I don't understand where the "10%" in your question comes from. However, the general rule is: whatever you get with no bonuses and improvements is enlarged by the sum of bonuses. In other words, if you'd normally get 100 of something and then you get two types of improvements, one 10% and one 20%, you get 100*(1+0.10+0.20)=130 (not 100*1.10*1.20=1.32=+32%, as it should be).
If this doesn't answer your question, please elaborate it, so we can try to help.
