This research report is identifying  ways to narrow the affordable housing gap in the next decade. This will require clear aspirations by policy makers to improve housing affordability and the use of four levers that we identify to unlock land in appropriate locations, reduce construction and operations costs, and improve access to low-cost financing. Together with an integrated and city-specific delivery approach, these measures can put housing within reach of households making 50 to 80 percent of their city’s median income. This document covers issues like challenges in affordability, reducing gaps in affordable housing, delivery of housing etc. decent housing for citizens is a perennial challenge for nations around the world. From slum residents in the developing world to middle-income households in expensive global capitals, hundreds of millions of people struggle to find decent housing that they can afford without severe financial stress. The economic and human toll of the housing affordability gap is enormous. We estimate that 330 million households are affected around the world and, under current trends, by 2025 the number of households that occupy unsafe and inadequate housing or are financially stretched by housing costs could reach 440 million—or 1.6 billion people. Access to decent, affordable housing is so fundamental to the health and well-being of people and the smooth functioning of economies that it is imbedded in the United Nations Universal Declaration of Human Rights. Yet in developing and advanced economies alike, cities struggle with the dual challenges of housing their poorest citizens and providing housing at a reasonable cost for low- and middle-income populations. In this report, we look at the dimensions of this problem—and how it will grow over the next decade—and offer a set of solutions that can narrow the affordable housing gap.