Drawing data from 64 sources, the 2021 Release includes seven years of data from 2013 to 2020. The Index is the most comprehensive look at states' preparedness to date. It is also the first national index that looks at the nation’s health security by collectively measuring the preparedness of the states. States face varying threats, apply preparedness principles in locally relevant ways, and have unique interdependencies. The display of results on the Index website takes into account both preparedness and model complexities.