dioxide. In general, these studies each follow a similar pattern: They posit a government program such as subsidies, government purchases, or contracts, to pro- mote a particular forest practice such as afforestation of agricultural land, modification of forestry management practices, or preservation of forestland, for a particular geographic context, which can vary in scope from sub- national to global. With the outline of the hypothetical program roughly in place, the analyses proceed to at- tach costs to the various inputs to production, include ing land, labor, and materials. In general, these studies have suggested that there are substantial opportunities for sequestering carbon in forests, perhaps on the order of 500 million tons per year in the United States alone (Richards and Stokes 2003). However, the cost estimates for achieving these high levels of sequestration range over two orders of magnitude, approximately from $5 to $500 per ton. This rather large range of costs exists in part because the analyses are based on different hypothetical pro- grams. One would expect different programs to have different costs. However, there are several other more subtle differences among the studies that lead to differ- ent costs estimates, some of which make comparisons among the studies problematic