1. The legal problems involved in instituting such a program or simulating it are not considered as part of this study.
2. The degree of substitutability is determined econometrically assuming Cobb-Douglas production functions.
3. The amount of carbon emited varies with the mode of transportation (boats, cars, trains, etc.) The 21.57 value is an averate for transportation based on the current transportation mix.
4. The amount of carbon generated depends on the fuel used to generate electricity. In Minnesota, 69.4 percent of the generation uses coal, and most of the rest uses nuclear energy (which does not emit carbon). The study used 18.81 tons of carbon (69% of the unit coal value).