Economics has been defined as the science of allocating scarce means among competing ends. Ultimate ends to be achieved may be defined as well-being, satisfaction, utility, or quality of life. It has become fashionable to divaricate economics into dimensions of efficiency and equity. Defined as increasing the size of the pie of goods and services, efficiency has received the lion's share of attention by economists; its study has been viewed as objective, precise, and respectable. Economists have relied heavily on perfect competition as a norm of efficiency, but perfect competition results only in a Pareto optimum. Using the Edgeworth Box as an example, two individuals or groups can be at a Pareto optimum on a contract curve, yet one individual or group can be in misery from starvation while the other individual or group can be satiated with goods and services. To move along the contract curve to a point of global welfare maximization requires knowledge of the marginal utility of additional goods and services (income). Utility is maximized at the point where marginal utility of income is equalized. Suggestions for such movement have been eschewed by positive economists in part because subjective, normative, interpersonal comparisons of utility were required and in part because, even if accurate estimates of marginal utility were unavailable, a normative judgment is implied that such movement is appropriate. It is time to begiin merging equity and efficiency in economic science, the nexus being the marginal utility of income. Given that economics is concerned with increasing wellbeing of people, the study of conventional measures of efficiency is neither objective nor precise because it conveniently assumes away too much by employing the premise that the marginal utility of income is equal for all income levels and all people. Neither is it appropriate to label the study of equity as unsuitably subjective and imprecise in view of advances in methodology that can provide useful comparisons of quality of life among populations defined by income, age, education, etc. Although methods for estimating m rginal utility may yet be too imprecise to make interpersonal comparisons of the marginal utility of income, the methodology appears to be sufficiently advanced to make useful intergroup comparisons of utility for formulating public policies that impact unevenly on dif erent groups. If the marginal utility of income is less for gain rs than for losers, it is possible that some public programs implemented on the basis of favorable conventional benefit-cost (B-C) ratios may in fact reduce well-being. To promote a nexus between equity and efficiency, an efficacious start is to replace the concept of economic efficiency implicit in benefit per unit of cost (B-C ratio) with the concept of social efficiency defined as satisfaction per unit of sacrifice. Social efficiency is similar in concept to economic efficiency except that dollar benefits are weighted by marginal utilities among gainers to indicate satisfaction, and dollar costs are weighted by marginal utilities among those paying the cost to arrive at total sacrifice. Wilmer M. Harper is with the Department of Agricultural Economics, New Mexico State University, Las Cruces, and Luther G. Tweeten is Regents professor, Department of Agricultural Economics, Oklahoma State University. Journal Article J-3357 of the Oklahoma Agricultural Experiment Station.