The markets are neither 100% efficient nor 100% noisy. There is a happy medium somewhere in between. An indirectly related, but telling anecdote: In their fina

The markets are neither 100% efficient nor 100% noisy. There is a happy medium somewhere in between. An indirectly related, but telling anecdote: In their financial models, M&A bankers are often told to ignore stock prices 24 hours prior to a deal's announcement. Insider trades artificially raise the price during this time.