%0 Journal Article
%T The Evolution of Stock Market Efficiency in the US: A Non-Bayesian Time-Varying Model Approach
%A Mikio Ito
%A Akihiko Noda
%A Tatsuma Wada
%J Quantitative Finance
%D 2012
%I arXiv
%R 10.1080/00036846.2015.1083532
%X A non-Bayesian time-varying model is developed by introducing the concept of the degree of market efficiency that varies over time. This model may be seen as a reflection of the idea that continuous technological progress alters the trading environment over time. With new methodologies and a new measure of the degree of market efficiency, we examine whether the US stock market evolves over time. In particular, a time-varying autoregressive (TV-AR) model is employed. Our main findings are: (i) the US stock market has evolved over time and the degree of market efficiency has cyclical fluctuations with a considerably long periodicity, from 30 to 40 years; and (ii) the US stock market has been efficient with the exception of four times in our sample period: during the long-recession of 1873-1879; the recession of 1902-1904; the New Deal era; and the recession of 1957-1958 and soon after it. It is then shown that our results are partly consistent with the view of behavioral finance.
%U http://arxiv.org/abs/1202.0100v13