Internal estimation and controlled selection with applications to sheep

Summary This paper examines the relationship of economic weights, a_i, with a general economic value surface. It is inferred that the a_i may vary across the population, as they can depend on the mean vector for the characters of interest. It is shown how these ideas extend to provide simple mechanisms for controlled selection. The problem of estimation is raised, and it is suggested that the procedures can be efficiently implemented, even in small populations, by a system of internal parameter estimation. This makes the entire selection programme independent of externally generated estimates of genetic parameters.