That is a complex question, so it will be difficult to deal with it in its entirety in a few minutes.
You mentioned a lower tax rate for small businesses. But SMEs form a very varied group that include some businesses that are showing strong growth, young businesses, businesses that are investing heavily, other businesses that one might call “mom-and-pop” operations like convenience stores, which have no growth objectives, and incorporated professionals. In short, businesses come in all shapes and sizes and they react to incentives differently.
A lower tax rate would be very helpful for innovating and young businesses, those that want to grow. For incorporated professionals, it is mostly about tax planning, which is not necessarily the right way to grow the economy. For family businesses too, it is not going to contribute to economic growth. So you have to be careful there.
The C.D. Howe Institute proposal is that a lower tax rate be more targeted to young businesses that are making investments and that wish to grow. With a better target, that tax option could bring about growth.