Much of the supply-side, fiscally conservative economic policies of Margaret Thatcher, Ronald Reagan, and even Mike Harris in Ontario were predicated on the belief that high income tax rates discourage work.  Cutting income tax rates would, it was argued, stimulate incentives to work and thereby increase economic growth.  Demonstrate an income tax cut leading to greater labour supply in a labour-leisure trade-off model.  What does this outcome assume about the relative sizes of the income and substitution effects?