Time series momentum in the US stock market: Empirical evidence and theoretical analysis

There is much controversy in the academic literature on the presence of short-term trends in financial markets and the trend-following strategy’s profitability. We restrict our attention to studying the time series momentum in the S&P Composite stock price index. Our contributions are both empirical and theoretical. On the empirical side, we present compelling evidence of the presence of short-term momentum. For the first time, we suppose that the returns follow a p-order autoregressive process and evaluate this process’s parameters. On the theoretical side, we develop a tractable theoretical model that contributes to our fundamental understanding of the trend-following strategy’s risk, return, and performance. Using our model, we also estimate the power of statistical tests on the trend-following strategy’s profitability and find that these tests suffer from the low power problem.