Our estimate that 85% of all health research is being avoidably “wasted” [Chalmers & Glasziou, 2009] commonly elicits disbelief. Our own first reaction was similar: “that can’t be right?” Not only did 85% sound too much, but given that $200 billion per year is spent globally on health and medical research, it implied an annual waste of $170 billion. That amount ranks somewhere between the GDPs of Kuwait and Hungary. It seems a problem worthy of serious analysis and attention. But how can we estimate the waste?