In Chapter 13, we examine the notion that population is important for national power, an idea widely recognized among scholars but rarely explored empirically. We begin by laying out a theoretical rationale, highlighting the notion that enhanced numbers of people should bring greater returns. Specifically, we emphasize that people provide economic resources, human capital, and innovation. Together, the greater capital, human capital, and innovation that a large population affords allows a society to produce more, which should promote greater self-sufficiency. In the analytical sections, we explore these hypotheses systematically across economic, military, and cultural dimensions of power. We find that size is associated with higher GDP, greater iron and steel production, and lower import and aid dependence. In addition, more populous countries tend to have more military personnel, higher military expenditures, and greater naval tonnage. Finally, larger countries have a greater number of universities, more patent applications, and more tourists. Our empirical analyses, coupled with analyses conducted by other scholars, thus place the thesis that size brings power beyond much doubt.