A nice illustration of how chaotic electronic health record data can be when aggregated across a large number of hospitals.
Earl F. Glynn, Mark A. Hoffman. Heterogeneity introduced by EHR system implementation in a de-identified data resource from 100 non-affiliated organizations. JAMIA Open, 2019 Aug 7, 2(4), 554-561. doi: 10.1093/jamiaopen/ooz035. Available in html format or pdf format.