The marginal effective tax rate, as best I can explain it, is the tax rate that applies to the last dollar of investment, the marginal dollar of investment. It's shorthand way economists look at this. If you have that dollar to invest, what country will you invest it in? Certainly, among the G-7 countries, Canada has the lowest meter, by a significant amount.
On December 1st, 2011. See this statement in context.