Canada is poised to cut its corporate-tax rate to 16.5% on Jan. 1, part of a decade-long campaign that some experts say is making the country one of the most cost-effective places to do business in the developed world.

Canada's government says the cuts and other business-attracting measures should bring more investment to the country. Economists say it's tough to figure out what the actual effects of such moves are, though some companies say Canada's relatively low taxes and stable financial and regulatory environment swayed...