Here Herman Daly unleashes a savage attack on the innocent Cobb-Douglas production function:
A large residual indicates weak explanatory power of the theory being tested–in this case the Cobb-Douglas theory that production increase is due only to capital and labor increase. But instead of being embarrassed by a large unexplained residual, some economists were eager to “explain” it as an indirect measure of technological progress, as a measure of improvement in total factor productivity. But is technology the only causative factor reflected in the residual? No, there are surely others, most especially the omitted yet rapidly increasing flow of natural resources, of energy and concentrated minerals. The contribution of energy and materials from nature to production is also part of the residual, likely dwarfing technological improvement. Yet the entire residual is attributed to technology, to total factor productivity, or more accurately “two-factor” productivity, in the absence of natural resources, the classical third factor.