Time-In-Cell 2019: A Snapshot of Restrictive Housing based on a Nationwide Survey of U.S. Prison Systems is the fourth national survey of its kind co-authored by the Correctional Leaders Association (CLA), formerly known as the Association of State Correctional Administrators (ASCA), and by the Arthur Liman Center for Public Interest Law at Yale Law School. The topic is “restrictive housing,” often termed “solitary confinement,” and defined as separating prisoners from the general population and holding them in cells for an average of 22 hours or more per day for 15 continuous days or more. This report estimates that between 55,000 and 62,500 prisoners in the United States were held in restrictive housing as of the summer of 2019. Time-In-Cell 2019 is based on survey responses from thirty-nine state prison systems providing data on 825,473 prisoners. These states reported housing a total of 31,542 individuals—or 3.8% of the total prison population in those jurisdictions—in solitary confinement. Across the set of thirty-nine states, percentages of the prisoners held in isolation varied from 11% to none, as four states said they no longer keep anyone in those conditions. The length of time individuals spent in restrictive housing varied widely. In the thirty-three states that captured this information, they reported that 46% of the individuals held in solitary confinement were there for three months or less. At the other end of the spectrum, almost 3,000 people—or 11% of all the people for which statistics were provided—had been kept in solitary confinement for more than three years. Two areas of special concern are the impact of mental illness and race on placement in restrictive housing. Using their own definition of “serious mental illness,” 33 states reported a total of more than 3,000 SMI prisoners in solitary confinement. Six jurisdictions reported that more than 10% of their prisoners in solitary confinement had a serious mental illness. Aggregating the numbers from 32 states and disaggregating by gender, Black and Hispanic men were somewhat more likely to be put into restrictive housing than white men: 43% of Black men and 17% of Hispanic men were in restrictive housing, compared to 40% and 15% respectively in the total male custodial population. Black women were much more likely to be placed in isolation: 42% of women reported to be in solitary confinement were Black, as compared to 22% of the total female custodial population. The report also provides an overview of litigation, legislation, and policy developments regarding the use of restrictive housing since 2018 both within and beyond the United States. Many of these changes focus on limiting the use of isolation for pregnant women, juveniles, and seriously mentally ill individuals.Time-In-Cell 2019 compares the responses of the 33 prison systems that answered the CLA-Liman surveys in 2015, 2017, and 2019. See ASCA-Liman, Reforming Restrictive Housing: The 2018 ASCA-Liman Nationwide Survey of Time-in-Cell, SSRN No. 3264350; ASCA-Liman, Aiming to Reduce Time-in-Cell (Nov. 2016), SSRN No. 2874492. Comparing percentages of prisoners held in restrictive housing in the 33 jurisdictions reporting during the last five years, the median was 4.9% in 2016; 4.0% in 2018, and 3.4% in 2019. The data in this report was collected before COVID-19, which in the future will introduce complicated questions about what distinguishes restrictive housing conditions from medical quarantine. These topics must be addressed by further research.