IPO relative difficulty, M&A option and size effect

Size effect in the Chinese stock market is huge from 2012 to 2017. We empirically identify a driving force behind the effect: M&A option caused by IPO and M&A policies changes. We show that the M&A frequency increases and the acquirers' market value deceases as the IPO relative difficulty rises, small firm premium is positively related to both IPO relative difficulty and M&A frequency, and among the listed firms that have stronger tendency to merge or acquire a private firm, size effect is significantly larger. These results hold when controlling reverse merger probability. In sum, we reveal a new mechanism: Compared with a large public firm, a small one is more likely to acquire a private firm with discount since both the acquired and the acquirer benefit more, so the stock price of a small firm contains a larger part of M&A option. This option value increases as IPO relative difficulty rises.