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The nonfarm work participation decisions of married men and women in rural Northern Ghana were jointly and separately estimated for married couples through a bivariate probit, using recent survey data. Selectivity bias was corrected for in estimating wage offer and labor supply equations, using Heckman's procedure. Education, experience, infrastructure, distance to the capital, and population density, as well as interactions between education and infrastructure and between education and distance to the city, were found to be significantly related to the probability of nonfarm labor market participation, wages, and the amount of nonfarm labor performed, with significant differences by gender.

A variance components methodology is developed for joint tests on a sample of time series of prices for seasonal differences in the price integration of markets. The approach requires a statistically adequate number of observations for each market within seasons characterized by constancy of transactions costs among markets. The model is applied to eighteen months of weekly grain prices for twenty-two villages in northern Nigeria. Results suggest that markets are not well integrated in the six months covering the harvest period. Implications are drawn for research on market performance in the region.

Ox-powered cultivation is common in parts of the Sahel, yet most farmers in the region continue to cultivate manually. Insights from oxen farms in Mali are compared to nonadopters in Upper Volta. Ox-driven technology in the Sahel may be more labor shifting than labor saving. Linear programming models indicate a prohibitive opportunity cost of extra labor required for team maintenance and use on small, rainfed farms growing traditional millets and sorghums in Upper Volta. Farm simulations suggest that ox plowing increases cash crop acreage, but clearly profitable adoption requires companion innovations to boost labor productivity in peak periods.

Indicators of efficiency and incentives derived from trade theory, such as the domestic resource cost coefficient (DRC) and effective protection (EP), are generally presented as simple means. Analysis of their distributions, using farm data on millet and sorghum production from West Africa, shows them to be highly variable and, in some cases, to be significantly skewed. The analysis also shows the indicators to be highly elastic to changes in such parameters as input and output prices. If this variability is not considered when making inferences from such data, policy recommendations can be seriously misleading because they are based on different farming populations.