But over the past decade, quality measurement efforts moved away from volume. Volume was obviously just a proxy. What we cared about was good outcomes, and if we could measure outcomes directly, why bother with volume? Although high-volume centers may be, on average, better than low-volume centers, surely there are some poor-performing, high-volume centers and well-performing, low-volume ones. So the thinking was that we could dispense with volumes if we could directly measure outcomes such as mortality and complications.