The Economist discusses the difficulty of getting an accurate number when it comes to outsourcing.
No one knows the exact size or shape of offshoring. There is no doubt that firms today use outside suppliers (some of them overseas) to do many of the things they once did themselves. These range from running call centres supplying customer services to payroll processing, software engineering and even research and development. Last month the McKinsey Global Institute, the consulting firm's internal think tank, published a report on the subject. Called "The Emerging Global Labour Market", it began by saying, "So far, the debate about offshoring has been fuelled by anecdote rather than fact," and then set about gathering hard data.