Especially in developing countries, natural resources and the environment are not optimally managed. Even so, it is possible for green accounts based on current prices to measure the realized contributions of the environment to net product. The prices for use in the green accounts, however, are not necessarily shadow prices as would be recommended by cost–benefit analysis: in practice, green or comprehensive NNP is an approximation of an index of welfare. The fact that a linearization of generalized national income is used implies that disaggregated, partial-equilibrium models of resources are useful.