Does the Existence of ‘Pump-and-Dump’ Schemes Contradict the Weak Form of EMH?

Yes, pump-and-dump schemes strongly contradict the Weak form of EMH. These schemes involve coordinated buying to artificially inflate a price (pump) and then selling at the peak (dump).

The price movement is not random but manipulated based on coordinated actions and false information. If traders can profit consistently from identifying and acting on these patterns, it suggests past price and volume data is not fully random.