The trick for governments is of course to know what levels of tax rate will produce the highest revenue - ie the peak of the Laffer curve.
If people think tax rates are too high, they will try and think up ways of avoiding paying them - and the wealthier you are, the more you have to lose, so the more likely you will try to avoid/evade paying the tax.
That's one reason why flat rate tax schemes tend to produce proportionately higher levels of revenue - they are perceived to be fair, so people quite happily pay them.
We are also in a position now where it wouldn't be too onerous to have banded VAT on a wider range of goods, enabling people to have much more control over the tax they pay through their economic activity. Again, this is likely to be seen as fairer, thus raising the total revenue even though the actual tax rate on some things would be lower.
