Bubble Necessity Theorem
arXiv:2305.08268 · doi:10.1086/732528
Abstract
Asset price bubbles are situations where asset prices exceed the fundamental values defined by the present value of dividends. This paper presents a conceptually new perspective: the necessity of bubbles. We establish the Bubble Necessity Theorem in a plausible general class of economic models: with faster long-run economic growth () than dividend growth () and counterfactual long-run autarky interest rate () below dividend growth, all equilibria are bubbly with non-negligible bubble sizes relative to the economy. This bubble necessity condition naturally arises in economies with sufficiently strong savings motives and multiple factors or sectors with uneven productivity growth.