This paper examines empirically whether the short-swing rule (Section 16b of the Securities Exchange Act) deters managers from trading before mergers. Since a merger forces the sale of the target's outstanding equity, insider purchases within six months before the merger cannot escape this rule. We examine the 1941–1961 period when no other insider trading laws were enforced. Consistent with 16b's deterrent effect, managers' purchases drop significantly before the announcement. Before completion, the decrease occurs only in the 1941–1955 period. Surprisingly, pre-announcement sales do not decline, even though 16b cannot punish deferral of planned sales.
Earlier evidence concerning the relation between stock returns and the effects of size and earnings to price ratio (E/P) is not clear-cut. This paper re-examines these two effects with (a) a substantially longer sample period, 1951-1986, (b) data that are reasonably free of survivor biases, (c) both portfolio and seemingly unrelated regression tests, and (d) an emphasis on the important differences between January and other months. Over the entire period, the earnings yield effect is significant in both January and the other eleven months. Conversely, the size effect is significantly negative only in January. We also find evidence of consistently high returns for firms of all sizes with negative earnings.