The United Nations Industrial Development Organization (UNIDO) Guidelines method values all costs and benefits in terms of changes in consumption values and uses a discount rate appropriate to valuing the social time preference for consumption. Importantly, this means that all investment has to be valued in terms of its forgone consumption values—typically significantly larger by a factor that could be more than double the investment. This approach also arose out of a central planning framework for government decision making that postulates that decision makers decide key economic parameters (such as the discount rate) rather than these being determined by and estimated from markets.
The Little-Mirrlees method values costs and benefits in terms of border or world prices in foreign exchange units (Little and Mirrlees 1969, 1974). Using world prices to anchor the values in a project had some attraction at the time, given the highly distorted nature of most economies. Although this is an attractive approach to dealing with the value of traded goods, it then requires that all nontraded goods and labor be converted to their foreign exchange equivalent and that all distortions be expressed in foreign exchange units. This method advocated the use of a discount rate based on the return on forgone investment.
The Harberger approach values economic costs and benefits in terms of the “weighted aver-age” of the values of the demand and supply prices of the market responses to the project and measures values in domestic currency (Harberger 1971, 1972). Accordingly, changes in income cause changes in consumption and savings and investment so that the discount rate is a weighted average of the supply and demand prices of capital (typically significantly higher than a discount rate for consumption alone). All externalities of stakeholders, including taxes and subsidies, are measured in domestic prices. Similarly, the financial analysis of the project is measured in consistent units with the economic analysis. These practical and useful features of the Harberger method have led to its wide adoption in project appraisal internationally. Distributional analysis is also a component of this approach to disaggregate the gains and losses to all parties affected by a project and to identify potential basic needs externalities where a project supplies basic needs to the poor.
Following the publication of these various methodologies, significant controversy arose over the appropriate approach to economic analysis of projects. In 1977, Sjaastad and Wisecarver published a seminal article showing that the consumption-based approach (UNIDO guidelines) and the weighted average approach (Harberger) would give the same results if the appropriate adjustments were made to the consumption opportunity cost of investment under the UNIDO guidelines that recognized the market responses to the investment project. The issue then remained as to which approach was the most practical and useful. By the early 1990s, most project appraisal outside of Europe followed the Harberger approach.