It's a very complicated question. I challenge anyone here to show that tax revenue in Canada goes down when multinationals move abroad. The reason is that when multinationals move abroad through an offshore financial centre, to the extent those multinationals are more productive, economic activity in Canada is higher. So tax revenue from that increased economic activity is higher, and the dividends that flow back to Canada are also higher.
On May 15th, 2007. See this statement in context.