TICKER tape: it’s an enduring image of Wall Street. The paper is gone but the digital tape runs on, across computer and television screens. Those stock quotations scurrying by on CNBC are, for many, the pulse of American capitalism. But Sal L. Arnuk doesn’t really believe in the tape anymore — at least not in the one most of us see. That tape, he says, doesn’t tell the whole truth. That might come as a surprise, given that Mr. Arnuk is a professional stockbroker. But suddenly, and improbably, he has emerged as a leading critic of the very market in which he works. He and his business partner, Joseph C. Saluzzi, have ... (full story)