it would be preferable to increase the addon payments for difficult cases to progressively eliminate these disparities as drg payments could allow only a partial reduction of the heterogeneity of patients across establishments milcent a veran they may also give incentives to optimise the reporting of activity and overstate the difficulties of each patient in france drg groups capture less than half of patients heterogeneity milcent b and upcoding ie deliberately overstating the casemix appears significant as in the united states milcent a and b dafny moreover as in primary care the payment structure provides little incentive for prevention and coordination between care providers