This project is an atypical one for research in physics, although the kind of questions we ask are quite common in other research areas. In mathematics, for example, it can happen that an entire field is constructed on a hypothetical basis: “Assuming this yet unproven theorem to be true, we can show that…”. The numerous theorems that are dependent on Fermat’s last theorem are a famous example, and were an important motivation to hunt for the final proof of that theorem. Similarly, modern solid-state physics increasingly depends on insights and numbers that are obtained with density-functional theory (DFT). If there would be problems – conceptual or practical ones – related to the reliability of the methods and codes that incarnate DFT, then a part of our solid-state knowledge would collapse. Surprisingly, there are many aspects about the reliability of DFT methods and codes that have never been systematically and quantitatively examined. Doing that, is exactly what this proposal is about.