Both numbers are most likely far higher.
Lower rates, do not lead to tax evasion by itself. Its simply, and patently ridiculous.
And as Gustaf asked, How would you stop this?
Raising the rate back to 95% won't magically make it happen, in fact it will be much worse with a higher rate.
You can riddle your tax code with penalties, fines, and punishments for this, but that only serves to make the tax code more complex encouraging those who can to avoid it and those who can't to make mistakes. Ironically the middle and working class takes the hit here.
Back in 2007, the Democrats tried to focus on the "tax gap" as a way to fund their wish list, and to facilitate class warfare rhetoric in the 2008 election. Then when it came down to actually solving the problem, those dumbos didn't have the first clue how to fix the problem that didn't involve spending large sums on enforcement (potentially more then could be realistically gained) or adding complexity to an already ridiculously complex tax code (which could lead to a larger "tax gap"). The hearings on it were deliciously amusing or about as amusing as a hearing on C-SPAN could be, and the reason was that they didn't have a clue.
I know what the solution is, or rather the most realistic solution that will generate the most revenue and not be counterproductive as there is no 100% solution. I think Gustaf knows what the "best" solution to the tax gap is, as well. And it has a fairly good record of success when tried, but of course it is difficult to acheive because the status quo is much preferred by special interests. The trouble for you is that you can't do this and at the same time use the tax code as a tool for the advancement of an anti-production, anti-wealth bias.
You can maintain some level of progressivism in the rates, of course, but not the level you desire.
