Book excerpt: Since many policymakers aspire to pull their countries out of the middle-income trap and into the ranks of high-income countries, they must understand the factors that hinder or support the transition. This book defines the middle-income trap and examines the roles of manufacturing, finance, and trade openness in achieving sustainable development. The book also explores the role of government policy in fostering growth in the People's Republic of China. A common theme is that such policies may have unforeseen side effects that undermine their effectiveness, including how the hukou registration system and land-use policy control the pace of urbanization.