The determination of the optimal values of input values to achieve a desired outcome is the subject of maximization theory. Marginal analysis is concerned with the determination of the point where one additional value of an input variable no longer produces an increase in the value of a desired output. It is possible to determine the optimal values for a group of input variables or for a single variable for the most efficient production of a desired output with the use of combination theory and marginal analysis. "The optimal number of traffic deaths in the United States is zero," as an example, should not be inferred to mean that an optimum model for the reduction of traffic deaths would attempt to eliminate all traffic deaths from the United States. The cost of enforcing speed limits, effects on productivity in the economy, and other related factors would be assessed as input variables to determine the point at which additional inputs of the variables failed to further reduce traffic deaths. A policy that only considers speed limits as an input variable could reduce traffic deaths to zero if the speed limit is reduced to zero. The cost to the economy and even the cost in lives for people who can't get health assistance if they need it would outweigh the value of reducing traffic deaths to zero.