What is Time-Varying Covariates

Accurate measurement of digital divides is important for policy purposes. Empirical studies of broadband subscription gaps have largely used cross-sectional data, which cannot speak to the timing of technological adoption. Yet, the dynamics of a digital divide are important and deserve study. With the goal of improving our understanding of appropriate techniques for analyzing digital divides, we review econometric methodology and propose the use of duration analysis. We compare the performance of alternative estimation methods using a large dataset on DSL subscription in the U.S., paying particular attention to whether women, blacks, and Hispanics catch up to others in the broadband adoption race. We conclude that duration analysis best captures the dynamics of the broadband gaps and is a useful addition to the analytic tool box of digital divide researchers. Our results support the official collection of broadband statistics in panel form, where the same households are followed over time.