Paying for performance: neither the end of the beginning nor the beginning of the end.

The extent of our ignorance about the effectiveness of incentives of various kinds on the behaviour of physicians and other healthcare professionals is alarming. The paper by Pink et al. illustrates some but by no means all of these lacunae. Not only is there a lack of reliable evidence about the immediate effects, but also the consequential effects for the health of patients or on quality of care in general are poorly understood. Some of the reasons for this are explored here, and a suggestion is made about how to improve matters in the future.