I could offer a couple of comments. When we do our analysis, because we try to base it on useful life, we look at considerations such as what the engineering life of the asset is and how long it could last physically. Then what gets added into that is questions of obsolescence—whether a product is becoming obsolete because of new products coming onto the market. As well, we look at whether a particular asset requires frequent upgrades and the extent to which those impinge upon the return the asset generates.
We here in Canada have tended to follow this idea of having rates reflect useful life fairly closely. In recent years, certain other countries have a similar approach. Some other countries—the United States being an example—do not take the same approach. The U.S. have tended to use their tax depreciation allowances more as a tool of economic development.
As Nancy said earlier, we have taken an approach whereby we try to provide a broadly neutral and efficient tax system that will then allow us to lower our tax rates and have the system be competitive on a broad basis. The United States, by comparison, has fairly high corporate tax rates with targeted tax incentives.