At what point would a common currency be more economically advantageous than two separate currencies? When the Canadian dollar is worth 85 US cents, there is still enough of a difference in the rate. However, as we head towards parity, the cost associated with having two currencies would be higher than for a single common currency. Have you already looked at this? When would it become more advantageous? Where would the exchange rate have to sit?
On May 1st, 2007. See this statement in context.