The competitive environment hypothesis revisited: Nonlinearity, nonstationrity and profit persistence

Much empirical lierature dealing with the competitive environment hypothesis tends to find nonstationary behaviour and very high persistence in time series of company profits. We model profit time series using a simple time series model that allows for nonstationary behavior over subsamples, but overall mean reversion. Using a new dataset constisting of profits for more than 150 US companies over a time period of 50 years, we present statistical evidence that the high persistence observed in profits when using linear autoregressive models is often due to the misspecification of the data generating process.