We study the adoption of Common Application membership by private four-year postsecondary institutions and its role in explaining the growth in undergraduate applications. Using data from the College Board's Annual Survey of Colleges, our estimation of proportional hazard models suggest that institutions respond to the net benefit of adoption. We estimate that membership increases applications by 5.7 to 7.0 percent and decreases yield rates by 2.8 to 3.9 percent. Acceptance rates decrease for members when their local networks are large. Membership is also associated with a decline in SAT scores and an increase in the percentage of students of color. Finally, falsification tests indicate that membership effects occur as a one-time adoption shock that persists thereafter.