This paper proposes a dynamic version of the principle of ranking and selection of projects by their benefit cost ratios (BCRs). It permits a very simple and practical technique for adaptive sequential choice to provide incentives for self help, cost control, sharing and maintenance. We discuss...

Numerous examples show that some econometric software packages contain serious flaws, and that users cannot safely assume that their software is accurate. A brief survey of the fundamentals of computer arithmetic discusses the sources of numerical error and emphasizes that computer arithmetic is...

Sometimes numerical failure of an econometric software package is quite stark: a nonlinear procedure fails to converge; illegal arguments to a function cause an abnormal end; matrices cannot be inverted. Other times a package fails without warning, and these types of failures are particularly...