We searched for the institutional negative externality posited by the new economic case for immigration restrictions in a variety of ways in this book. We did not find it. In fact, instead we have often found that immigration creates a positive externality that improves institutions related to productivity. There are limitations to all of the methods we have employed in this book. Thus, there is no QED here. We cannot rule out that, in some cases, in some places, from some particular immigrant flows, that a negative externality that undermines formal and informal institutions or norms related to productivity does exist. However, in general, our findings should make scholars skeptical of how widely relevant the new case for immigration restrictions is. Thus, our findings also bolster the standard economic case for free immigration by increasing our confidence that most of the global economic gains that would stem from free immigration do, in fact, exist.