Ellison's uninterrupted leadership, coupled with the fact that he still owns nearly one-fourth of Oracle's stock, gives him a tight grip on one of the most powerful forces in the twenty-first century, controlling the means to information at thousands of major corporations. Oracle is, in effect, the largest public company that remains "privately held." Its dominance in the database, which resides at the center of corporations, has been compared to Microsoft's hold on the desktop, although the market share figures for the monopolist Microsoft are much higher. Still, as of year-end 2002, Oracle held 60 percent of the market for the Unix databases most large companies use and 39.4 percent of the overall market, according to market researcher IDC. More than half of the Fortune 100 cited Oracle as the preferred database vendor.