12 labor shortages caused by infection, especially so in endemic communities. Since GDEC activities have been typically prevalent in rural areas, the marginal product of labor is estimated as the additional output gained in the agricultural sector through increasing the supply of productive labor input.'<sup>3</sup> In order to estimate the additional output of labor accrued through prevention of Guinea worm infection, methods based on the Cobb-Douglas production function were used.'<sup>4</sup> The following parameters are considered relevant in estimating the additional output of labor in the agricultural sector: the number of cases of Guinea worm infection prevented by GDEC (the difference between the number of cases of Guinea worm without GDEC and with GDEC) in the productive age group, the productivity loss -- in terms of percent of work-year lost -- per case of dracunculiasis, the output elasticity of labor in the agricultural sector, and the length of the effective project horizon. As in the analysis of costs, output figures are measured in 1987 constant dollars for consistency of comparison between costs and benefits. The following subsections describe how each of these parameters was estimated.

# _Cases of Guinea Worm without GDEC_

Global 2000 estimates that in 1986 (i.e., prior to the initiation of GDEC activities) the annual worldwide incidence of dracunculiasis was in the vicinity of 2.2 million cases. For the benchmark case we assume that in the absence of GDEC, in the very least, the annual incidence would have remained at this level.'<sup>5</sup>

- 12 See Shulman (1985) for additional details regarding the coincidence of peak labor input demand with the dracunculiasis cycle and the precipitation cycle. In our paper we assume a work year of 40 weeks.

- _13_ We are assuming unemployment is _not_ a major factor in the analysis. Several surveys of labor markets in Sub-Saharan Africa have indicated that unemployment is largely an urban phenomenon. In fact, as Vandemoortele (1991) indicates, unemployment in the region _increases_ with educational and skill level. The rural labor sector (on which this study exclusively focuses) primarily comprises unskilled workers (with relatively low levels of education) as well as subsistence farmers. Therefore, increases in productive labor time _are_ expected to result in the augmentation of agricultural output.

- i This methodology follows that in Kim and Benton (1995) and Kim _et al._ (1997). The Cobb-Douglas function relates output Y to inputs E (effective labor input in efficiency units) and K (land/capital) in the following manner: Y = _AErKb,_ where A is a technology parameter. The parameters a and b represent the elasticity of output with respect to inputs: a, for example, is the percentage increase in output caused by a unit percentage increase in labor input. Also, a represents the labor share of output. Similarly for b. Constant returns to scale can be represented by the assumption _a+b = 1,_ which means that if both land and labor inputs increased by a certain proportion, then output would also increase by that same proportion: for example, a doubling of both labor and land inputs would yield double the output.

- _15_ In a subsequent section, we assess the sensitivity of our analysis to increases as well as decreases in the projected annual incidence of dracunculiasis over time in the absence of GDEC.

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