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Working Paper
A Robust Test for Weak Instruments with Multiple Endogenous Regressors
We extend the popular bias-based test of Stock and Yogo (2005) for instrument strength in linear instrumental variables regressions with multiple endogenous regressors to be robust to heteroskedasticity and autocorrelation. Equivalently, we extend the robust test of Montiel Olea and Pflueger (2013) for one endogenous regressor to the general case with multiple endogenous regressors. We describe a simple procedure for applied researchers to conduct our generalized first-stage test of instrument strength and provide efficient and easy-to-use Matlab code for its implementation. We demonstrate ...
Working Paper
The Returns to Government R&D: Evidence from U.S. Appropriations Shocks
Based on a narrative classification of all significant postwar changes in R&D appropriations for five major federal agencies, we find that an increase in nondefense R&D appropriations leads to increases in various measures of innovative activity and higher business-sector productivity in the long run. We structurally estimate the production function elasticity of nondefense government R&D capital using the SP-IV methodology of Lewis and Mertens (2023) and obtain implied returns of 150 to 300 percent over the postwar period. The estimates indicate that government-funded R&D accounts for one ...
Working Paper
The Returns to Government R&D: Evidence from U.S. Appropriations Shocks
We estimate the causal impact of government-funded R&D on business-sector productivity growth. Identification is based on a novel narrative classification of all significant postwar changes in appropriations for R&D funded by five major federal agencies. Using long-horizon local projections and the narrative measures, we find that an increase in appropriations for nondefense R&D leads to increases in various measures of innovative activity, and higher productivity in the long run. We structurally estimate the production function elasticity of nondefense government R&D capital using the SP-IV ...
Working Paper
Work from Home After the COVID-19 Outbreak
Based on rich novel survey data on almost 5,000 working age adults, we document that 35.2 percent of the workforce worked entirely from home in May 2020, up from 8.2 percent in February 2020. Highly educated, high-income and white individuals were much more likely to shift to remote work and to maintain employment following the virus outbreak. Using available estimates of the potential number of home-based workers suggests that a large majority (71.7 percent) of U.S. workers that could work from home, effectively did so in May. We provide some evidence indicating that apart from the potential ...
Working Paper
Mobility and Engagement Following the SARS-Cov-2 Outbreak
We develop a Mobility and Engagement Index (MEI) based on a range of mobility metrics from Safegraph geolocation data, and validate the index with mobility data from Google and Unacast. We construct MEIs at the county, MSA, state and nationwide level, and link these measures to indicators of economic activity. According to our measures, the bulk of sheltering-in-place and social disengagement occurred during the week of March 15 and simultaneously across the U.S. At the national peak of the decline in mobility in early April, localities that engaged in a 10% larger decrease in mobility than ...
Oil and Gas Sector Increasingly Influences U.S. Business Fixed Investment
As U.S. oil production has more than doubled over the past decade, the oil and gas sector has become more important to growth in non-residential investment.
Working Paper
Work from Home Before and After the COVID-19 Outbreak
Based on novel survey data, we document a persistent rise in work from home (WFH) over the course of the COVID-19 pandemic. Using theory and direct survey evidence,we argue that three quarters of this increase reflects adoption of new work arrangements that will likely be permanent for many workers. A quantitative model matched to surveydata predicts that twice as many workers will WFH full-time post-pandemic compared to pre-pandemic, and that one in every five instead of seven workdays will be WFH. These model predictions are consistent with survey evidence on workers' own expectations about ...
Commuting Patterns During COVID-19 Endure; Minorities Less Likely to Work from Home
Some workers transitioned to working from home relatively easily. In many jobs, however, performing regular work activities from home is impossible, forcing many individuals to become inactive or look for a new job.
Working Paper
Dynamic Identification Using System Projections and Instrumental Variables
We propose System Projections on Instrumental Variables (SP-IV) to estimate dynamic structural relationships using impulse responses obtained from local projections or vector autoregressions. SP-IV replaces lag sequences of instruments in traditional IV with lead sequences of endogenous variables. By allowing the inclusion of lagged variables as controls, SP-IV weakens exogeneity requirements and can improve efficiency and effective instrument strength relative to 2SLS. We provide inference procedures under strong and weak identification, and show that SP-IV outperforms conventional IV ...
Report
Measuring Real Activity Using a Weekly Economic Index
This paper describes a weekly economic index (WEI) developed to track the rapid economic developments associated with the onset of and policy response to the novel coronavirus in the United States. The WEI is a weekly composite index of real economic activity, with eight of ten series available the Thursday after the end of the reference week. In addition to being a weekly real activity index, the WEI has strong predictive power for output measures and provided an accurate nowcast of current-quarter GDP growth in the first half of 2020. We document how the WEI responded to key events and data ...