Why do corporations use them? In my experience, corporations generally are motivated to return profits to shareholders. That's their bottom-line objective most of the time: to benefit shareholders. They look to provide the highest after-tax returns possible, so they're looking for low tax rates. That's a reasonable objective for business people.
Our challenge at CRA is to make sure that profits attributable to Canada are properly reported in Canada, and that profits that belong to other countries, such as important trading partners like the United States, the Europeans, the Japanese and the Koreans, can be taxable appropriately in those countries as well.
We have some tools. Currently, we use transfer pricing rules consistently with other countries that require that intragroup transactions occur at arm's-length prices, so really at commercial terms within a multinational group across its supply chain.
My colleague Trevor mentioned the foreign accrual property income rules. Canada has a policy of requiring that passive income that's earned offshore by Canadian multinationals and Canadian high-income individuals is taxable on an accrual basis in Canada as a general matter.