Should interventions to reduce variation in care quality target doctors or hospitals?

Except for length of stay after hip replacement, no more than 11% of variation in case-mix adjusted performance indicators can be attributed to doctors and organisations with the rest reflecting random chance and unobserved patient factors. Doctor variation exceeds hospital variation by a factor of 1.2 or more. However, identifying poor performance amongst doctors is hampered by insufficient numbers of cases per doctor to reliably estimate their individual performances. Policy makers and regulators should therefore be cautious when targeting individual doctors in performance improvement initiatives.