Adoption lags tell us when a country first starts using a new technology, but they do not show how quickly that technology spreads within the country once it has arrived. To understand this second part of the story, we need to look beyond the moment of first adoption and examine how widely a technology is taken up overtime. Mestieri,24 it is possible to estimate the technology use intensity - that is, the share of potential technologies diffuse within countries after their initial introduction, and how the intensity and overall usage patterns of each technology vary across economies over time. economies has changed over time. From the 1800s through much of the 20th century, this gap generally widened. Although the pattern varies across individual technologies, newer technologies typically saw larger differences in how intensively they were used. Comin and aligns closely with the evolution of global income disparities in the 2oth century.