  This paper outlines a framework for the study of innovation that treats
discoveries as additions to evolving networks. As inventions enter they expand
or limit the reach of the ideas they build on by influencing how successive
discoveries use those ideas. The approach is grounded in novel measures of the
extent to which an innovation amplifies or disrupts the status quo. Those
measures index the effects inventions have on subsequent uses of prior
discoveries. In so doing, they characterize a theoretically important but
elusive feature of innovation. We validate our approach by showing it: (1)
discriminates among innovations of similar impact in analyses of U.S. patents;
(2) identifies discoveries that amplify and disrupt technology streams in
select case studies; (3) implies disruptive patents decrease the use of their
predecessors by 60% in difference-in-differences estimation; and, (4) yields
novel findings in analyses of patenting at 110 U.S. universities.
