There are a lot of articles on the pro's, con's, and strategies of hospital payment by DRG, and from as far away as Saudi Arabia (here).
Here's a German viewpoint, from an English article. See an article, "How to Save Germany's Hospitals," which describes the strategic need for long-postponed reforms. By Ben Knight; December 2022; here.
The long-postponed reforms are mostly framed as bad or perverse incentives arising from aspects of the DRG system.
See a 2017 article on the same theme by Knight, here.
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Knight's 2022 article springs, in part, from a recent 50-minute German-language television documentary about their hospital system.