Social discounting conventions vary widely. Some differences reflect institutional constraints, but many reflect differing assumptions about how a social discount rate should be derived and applied. The divide between advocates of social opportunity cost and social time preference (STP) frameworks seems unbridgeable. There is no consensus among STP advocates on whether the social cost of funding $1 of public spending is barely more than $1 of consumption or perhaps more than $2; or on whether the covariance of public service benefits with income merits a discount rate premium that is trivial or a few percentage points. The practicalities of government fund raising are sometimes overlooked. The issues are here reviewed in the light of the literature and of experience with developing and applying social discounting regimes and extended debates within government.

The productivity of herbicides used in corn and soybeans was calculated from field data collected in Ontario from 1967 to 1985. Combinations of preplant incorporated and preemergence treatments were selected and were evaluated to determine their effect on crop yield. Corn and soybean yields increased from herbicide use, thereby resulting in a positive net benefit to growers. Benefit/cost ratios for herbicide use in corn and soybeans were calculated to be 2.8/1 and 2.6/1, respectively, at an average price of $132/1000 kg for corn and $275/1000 kg for soybeans. The benefit/cost ratios varied with test location, method of herbicide application, and prevailing market price.