(Bloomberg Markets) -- On the 61st floor of the iconic 30 Rock building in Midtown Manhattan, Jim Rossman's team is embarking on a big data project this year. Its mission: analyzing shareholder ownership in a way that could help chief executive officers hang on to their jobs.

Rossman, who heads the corporate preparedness group at Lazard, has expanded his team globally to more than a dozen activist-defense bankers over the past three years. Among their tasks is a comprehensive study of every investor reporting holdings in any of 1,000 companies, including all of the S&P 500 constituents. The bankers are calculating how much of each stock is owned by an ETF, a mutual fund, a hedge fund, or other asset manager. That way, Rossman says, he can start to predict how influential an activist investor may be.

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