A recent study by Population Action International (PAI), The Shape of Things To Come: Why Age Structure Matters to a Safer, More Equitable World, provides a timely illustration of population trends and their current interpretations. The report seeks to demonstrate that in today’s changing world, investment in well-designed population and reproductive health policies can play an important role in advancing national and global development. Through their analysis of age structures and population pyramids across the world, Elizabeth Leahy and her co-authors guide the reader through the consequences of the demographic transition and changes in age structures, as well as their implications for economic growth. They also explore the impacts of changing age structures on security, democratic development, governance, vulnerability to civil conflict, and social well-being.