How does social distancing affect the spread of Covid-19 in the United States?

In recent weeks the country has begun to ease restrictions put in place to counter the Covid-19 pandemic.Consequently, it is important for policymakers and the public to understand the extent to which increasing levels of mobility among the population may lead to a rise in the spread of the disease.In this Chicago Fed Letter, we consider two key questions.First, how long does it take for changes in mobility rates to be reflected in new cases and deaths?A sound understanding of the timing of these lags can enable policymakers to monitor the effects of changing policies more effectively.Second, how does a change in mobility affect the reproduction number, R, of the novel coronavirus 2019 (Covid-19)?The better we are able to understand this relationship, the more we will be able to fine-tune social distancing policies to prevent surges in Covid-19 cases.Improving our understanding of the spread of the virus is important not only from a public health perspective but also from the standpoint of the economy.Future disease outbreaks may inhibit consumers and businesses from resuming activity either voluntarily or through the imposition of new government restrictions.Consequently, the Congressional Budget Office's economic forecast for the second half of 2020 incorporates various possibilities regarding mobility and the rate of spread of Covid-19, including the risk of a resurgence later this year. 1