I used to read The Economist a few decades back. It talked about a doctor shortage in Sweden. When the layers were pealed back, the 75% marginal tax rate had doctors working half days. They stayed home in the afternoon, cooking gourmet meals, fixing their cars, and doing home renos.

When the rate was reduced to 60%, the doctors came back to work full time. They hired mechanics and carpenters and ate in restaurants.

How far we can push the marginal tax rate is called the Laffer curve. At some point, the talented people start withdrawing their services from the economy. Canada seems to be below that curve with its 50-55% marginal tax rate.

But setting an appropriate tax rate doesn't apply to those business people who are good at tax avoidance and minimization. I would say many of them would say 15% is too much. Maybe we should charge them $10 every time they use a road.