Fort Hugo
Institute of Physics, Faculty of Science, Universidad de la República, Montevideo 11400, Uruguay.
Entropy (Basel). 2023 Jul 7;25(7):1029. doi: 10.3390/e25071029.
This paper starts by presenting an empirical finding in the U.S. stock market: Between 2001 and 2021, high productivity was achieved when the Shannon evenness-measuring the inverse of concentration-dropped. Conversely, when the Shannon evenness soared, productivity plunged. The same inverse relationship between evenness and productivity has been observed in several ecosystems. This suggests explaining this result by adopting the business ecosystem perspective, i.e., regarding the tangle of interactions between companies as an ecological network, in which companies play the role of species. A useful strategy to model such ecological communities is through ensembles of synthetic communities of pairwise interacting species, whose dynamics is described by the Lotka-Volterra generalized equations. Each community is specified by a random interaction matrix whose elements are drawn from a uniform distribution centered around 0. It is shown that the inverse relationship between productivity and evenness can be generated by varying the strength of the interaction between companies. When the strength increases, productivity increases and simultaneously the market evenness decreases. Conversely, when the strength decreases, productivity decreases and evenness increases. This strength can be interpreted as reflecting the looseness of monetary policy, thus providing a link between interest rates and market structure.
在2001年至2021年期间，当衡量集中度倒数的香农均匀度下降时，实现了高生产率。相反，当香农均匀度飙升时，生产率则大幅下降。在几个生态系统中也观察到了均匀度与生产率之间的这种反比关系。这表明可以通过采用商业生态系统视角来解释这一结果，即将公司之间的相互作用网络视为一个生态网络，其中公司扮演物种的角色。对这种生态群落进行建模的一个有用策略是通过成对相互作用物种的合成群落集合，其动态由洛特卡 - 沃尔泰拉广义方程描述。每个群落由一个随机相互作用矩阵指定，其元素从以0为中心的均匀分布中抽取。结果表明，生产率与均匀度之间的反比关系可以通过改变公司之间相互作用的强度来产生。当强度增加时，生产率增加，同时市场均匀度下降。相反，当强度降低时，生产率下降，均匀度增加。这种强度可以解释为反映货币政策的宽松程度，从而在利率与市场结构之间建立联系。
