I'm not so sure about this part. Why do you think it should be any particular ratio? I'm curious to know your reasoning. I'm not really sure how fx rates should be estimated other than just looking at historical data, which is probably not very smart.
Currency exchange rates over the short term are wacky and all over the place. There's a lot of speculation and emotion in the market place. The longer term valuation of currency is easier to calculate because it depends on a few major things:
1) Political and monetary stability - the US and Canada are both politically stable and have similar monetary policies (ie. target inflation rate banking with both countries aiming for 1 - 3% inflation). In fact, one could easily make a case that we are more stable than the US in many ways.
2) Purchasing power parity - simply the amount of any given basket of products that each currency can purchase. It takes more money to buy things in Canada vs the US for a few basic factors: we have a lower population density, we have a smaller market for goods, we are less innovative, we have less trading connections, we are
less productive (to the tune of ~80% of US productivity per capita), and we have a somewhat tighter controlled marketplace (more protected industries particularly in agriculture).
3) Interest rates - ties in with monetary stability in many ways. Canada and the US have similar interest rates so our assets are similarly attractive to foreign buyers. If interest rates in Canada were much higher than the US, the CAD would appreciate vs. USD because foreign investors would be buying Canadian debt instead of US debt eventually to the point where there would be no net benefit to buying Canadian debt due to CAD being more expensive. Currently our government pays lower long term bond yields than the US.
4) Economic condition/value - this refers to the general condition of the overall economy as well as our economic value in natural resources and human resources. If our economy is more attractive than the US economy investors will buy CAD to invest in Canadian companies, pushing up the value of the CAD.
I believe the CAD, over the long-term, should be valued somewhere around 90 cents. We are less productive, but have more natural resource value per capita, are more stable politically, and have a stable central bank. This is, of course, purely my own personal belief and I'm not a currency trader because I believe that currency valuations are erratic and change for no rhyme or reason.