The marginal benefit and cost of diversification for Florida orange producers is analyzed using certainty equivalents. Results indicate that for moderate and high levels of risk aversion, diversification into strawberry, grapefruit, or additional orange production is not optimal. However, moderately risk averse Florida orange producers can gain by diversifying into grapefruit production if the annual amortized fixed costs can be reduced by as little as 10 percent.

A standard result in the literature on monetary policy rules is that of certainty-equivalence: Given the expected values of the state variables of the economy, policy should be independent of all higher moments of those variables. Some exceptions to this rule have been pointed out in the literature, including restricting the policy response to a limited subset of state variables, or to estimates of the state variables that are biased. In contrast, this paper studies fully optimal policy rules with optimal estimation of state variables. The rules in this framework exhibit certainty-equivalence with respect to estimates of an unobserved state variable (“excess demand”) X, but are not certainty-equivalent when (i) X must be estimated by signal extraction and (ii) the optimal rule is expressed as a reduced form that combines policymakers' estimation and policy-setting stages. I find that it is optimal for policymakers to attenuate their reaction to a variable about which uncertainty has increased, while responding more aggressively to variables about which uncertainty has not changed.

The conventional linear/quadratic/Gaussian assumptions are modified in that minimisation of the expectation of cost G defined by (2) is replaced by minimisation of the criterion function (5). The scalar –θ is a measure of risk-aversion. It is shown that modified versions of certainty equivalence and the separation theorem still hold, that optimal control is still linear Markov, and state estimate generated by a version of the Kalman filter. There are also various new features, remarked upon in Sections 5 and 7. The paper generalises earlier work of Jacobson.