Short-Term Traders, Learning and Informational Externalities, 2015

Abstract: This paper examines how short term trading impacts the aggregation of information in financial markets. I develop a model where short-term traders, in an attempt to learn about the average beliefs of future market participants, make the price relatively more noisy. This typically introduces a negative informational externality on long-term investors. I show that (i) as the horizon of the informed traders decreases, the price becomes relatively less precise; (ii) an inflow of informed traders in the market can decrease the informativeness of the price when the traders have a relatively short horizon or the market is expected to be thin in the future; (iii) finally, as rational informed short-term traders have access to an extra source of information about the future price, they end up creating more noise and a decrease in the informativeness of the price might result. Thus, paradoxically, more informed trading could lead to a less informative price.