Those estimates were done by the Department of Finance using an economic model. Roughly speaking, the general approach...if we're looking at a dollar, for example, of construction spending, we look at how much a typical dollar of construction spending generates in additional output and employment in construction in the first instance. In the second instance, we look at the feedback impacts of that dollar circulating in the economy and the construction sector on other sectors. There's an annex in the budget that sets out our approach.
At a very high level, I guess what one observes from these economic studies is that a dollar spent on direct construction in the first instance generates more economic activity than a dollar related to a personal income tax cut, for example. They both have their roles to play, in that you can deliver personal income tax reductions ahead of infrastructure spending. They can be delivered immediately. However, the impact of a reduction in personal income taxes on the economy is, in the first instance, muted by a desire on behalf of householders who are likely to save part of that.
The general approach is to estimate what we call the “multiplier impact”, which is how much a dollar of spending your tax reduction generates in terms of additional activity and employment, and then using a model to determine the secondary impacts.
I might point out very quickly that when we did this work we compared our approach to the approach and the assumptions used by the U.S. government, and we asked both the Conference Board and the University of Toronto to verify our assumptions. We're comfortable that our approach was reasonably prudent. Having said that, these are estimates, and they are subject to error.