According to Gartner, [...] there are 250 billion lines of COBOL source code being used, with 15 billion new lines each year. A major AAA national company has some 35,000 COBOL modules plus supporting COPY books and so on in its inventory. A major airlines has 848 COBOL modules in its crew management system with some 3,000,000+ SLOC of code. Merrill-Lynch runs 70 percent of its daily business on COBOL systems.
via DDJ
Those numbers are quite staggering, and quite believable.
