Are ‘flow of ideas’ and ‘research productivity’ in secular decline?
通过构建思想流动和研究生产力两个指数，发现自20世纪50-70年代以来，欧美地区的科学知识产出持续下降，挑战了内生增长理论中知识指数积累的假设。
It is widely held true that fundamental scientific knowledge has been accelerating exponentially over the past centuries and will continue to do so for the foreseeable future. Moreover, endogenous growth theory postulates that this exponential accumulation of knowledge is the main source of the ubiquitous exponential economic growth. We test these claims by constructing two new series of knowledge indices, one representing the historical evolution of the Flow of Ideas, the other one giving a measure of Research Productivity, by combining Krebs (2008)s’ Encyclopaedia of Scientific Principles and Asimov (1989)’s Chronology of Science and Discovery. Three different geographical regions are covered: 1) Continental Europe, 2) the United Kingdom, and 3) the United States; and two disciplines: a) the physical sciences, and b) the life sciences. Starting in 1750, our indices reveal waves coinciding with the three industrial and technological revolutions, in particular in the United Kingdom. Our main result is that scientific knowledge has been in clear decline since the early 1970s for the Flow of Ideas and since the early 1950s for the Research Productivity, in the geographical regions and scientific disciplines covered by the indices. The decline is observed until the end of the dataset constructed by combining both Krebs’ encyclopaedia and Asimov's Chronology, that is 1988. Using only Krebs (2008)s’ Encyclopaedia of Scientific Principles, valid until 2007, the decline is further confirmed for the Research Productivity until 2007. Given the strong downward trends that we document up to 1988 for the combined dataset and which is also prominent in the Encyclopaedia of Scientific Principles until 2007, there is no visible sign of an inflection that would signal the initiation of a reversal. Overall, our results support the Kuhnian theory of knowledge creation through scientific revolutions, punctuation and paradigm shifts and falsify the gradualism that lies at the basis of the currently prevailing economic paradigm of endogenous growth.