Characterizing collective physical distancing in the U.S. during the first nine months of the COVID-19 pandemic (preprint)

The COVID-19 pandemic offers an unprecedented natural experiment providing insights into the emergence of collective behavioral changes of both exogenous (government mandated) and endogenous (spontaneous reaction to infection risks) origin. Here, we characterize collective physical distancing -- mobility reductions, minimization of contacts, shortening of contact duration -- in response to the COVID-19 pandemic in the pre-vaccine era by analyzing de-identified, privacy-preserving location data for a panel of over 5.5 million anonymized, opted-in U.S. devices. We define five indicators of users' mobility and proximity to investigate how the emerging collective behavior deviates from the typical pre-pandemic patterns during the first nine months of the COVID-19 pandemic. We analyze both the dramatic changes due to the government mandated mitigation policies and the more spontaneous societal adaptation into a new (physically distanced) normal in the fall 2020. The indicators defined here allow the quantification of behavior changes across the rural/urban divide and highlight the statistical association of mobility and proximity indicators with metrics characterizing the pandemic's social and public health impact such as unemployment and deaths. This study provides a framework to study massive social distancing phenomena with potential uses in analyzing and monitoring the effects of pandemic mitigation plans at the national and international level.

The COVID-19 pandemic amplified long-standing racial disparities in the United States criminal justice system (preprint)

During the first year of the COVID-19 pandemic, the number of incarcerated people in the United States decreased by at least 16%---the largest, fastest reduction in prison population in American history. Using an original dataset curated from public sources on prison demographics across all 50 states and the District of Columbia, we show that incarcerated white people benefited disproportionately from this decrease in the U.S. prison population, and the fraction of incarcerated Black and Latino people sharply increased. This pattern deviates from a decade-long trend before 2020 and the onset of COVID-19, during which the proportion of incarcerated Black people was declining. Using case studies of select states, we explore and quantify mechanisms that could explain these disparities: temporary court closures that led to fewer prison admissions, changes in the frequency of police interactions, and state-level prison release policies that sought to de-densify congregate settings. These findings illuminate how systemic racism pervades juridical and penal institutions and is the engine of mass incarceration in America.