The researchers evaluated how well a system called BJ-DRGs, used in Beijing hospitals to group patients with similar diagnoses for billing purposes, performed in terms of cost. They looked at 1.3 million patient records from 149 hospitals in Beijing in 2008. The BJ-DRGs system showed the best results for controlling costs compared to other systems. This means that under Beijing's medical information conditions, BJ-DRGs worked well for managing expenses.