We show that in multi-sector optimal growth models, where the technology satisfies a simple reachability condition, infinite horizon programs which satisfy the competitive conditions are optimal. We provide examples of a variety of production models where the reachability condition is satisfied....

The article discusses Wicksell's assessment of the controversy between Bohm-Bawerk on one side, and Fisher and Bortkiewicz on the other, on the role of productivity (the 'third reason') in the determination of the rate of interest. It is shown that in the process of arguing out the third reason...