[quote=@TheSovereignGrave]
Just guesstimate! It's what I'm gonna do.
[/quote]

This guy gets it.

And this logic can also be applied to your trade revenue. If you're doing a lot of trading (which I don't think anyone is at the moment?) then it'd probably be like 20-30%? Depending on how lucrative and dependant you are on the trade, of course. 

But perhaps you are right, maybe it's a detail not worth bothering with. I could walk the middle ground, and leave it as an optional detail.