My point is that for taxation or legislation you need exact numbers and the same number should be the result for two different people in the same situation. I a

My point is that for taxation or legislation you need exact numbers and the same number should be the result for two different people in the same situation. I agree that even huge margin errors could be perfectly fine (because some value + margin error still give you lower bound) but I think we're not even close to that. Plus as much as I want it I just don't see how would you ever implement anything practical. Pure sophistication and obfuscation helps hide the wealth. Somebody rick can easily spend 10% of their wealth doing that (we're talking millions here) and tracing back these paths can turn out to be more expensive. Gov is at huge disadvantage here despite laws already helping it in a very questionable ways - like your need to prove where did you get some money from instead of gov proving that you got it illegally.