It’s simple: Phase II and Phase III trials need a lot of patients. Therefore, they need a lot of research sites. And clinical trials that need a lot of patients and sites are also likely to be in multiple towns, cities, and states as no one location will be able to provide enough patients. In 2020, for example, the average Phase III trial had at least 24 sites, leading to the conclusion that the average Phase III trial that year was spread across several states.
White Paper