“…In general, more has been written about costs than about returns. If one looks at the continuum from models to methods to technologies, several authors (see, for example, Cullen, Sawzin, Sisson, and Swanson, 1978;Head and Buchanan, 1981;Kearsley and Compton, 1981;Mirabal, 1978;Swanson and Gradous, 1988) have provided models or classification schemes for costs, and many (Head, 1985;Kearsley, 1982;Mirabal, 1978;Roden, 1984) have developed methods to accompany these models. However, as mentioned before, neither the models nor the methods are complete.…”