Buy on rumours - sell on news: a manipulative trading strategy

A trader who receives a signal about a future public announcement can exploit this private information twice. First, when he receives his signal, and second, at the time of the public announcement. The second round advantage occurs because the early-informed trader can best infer the extent to which his information is already reflected in the current price. This paper shows that early-informed traders trade very aggressively at the time they receive their signal. They try to manipulate the price in order to enhance their informational advantage at the time of the public announcement. In addition, they speculate by building up a position in period one, which they partially unwind 'on average' in period tow. The analysis shows that informational leakage makes prices prior to public announcements more informative but reduces informational efficiency in the long run.