This book is of interest to economists working in applied demand analysis, marketing professionals studying product substitution and complementarity, and policymakers evaluating the effects of taxes, subsidies, and regulatory interventions on consumer behavior. Applying the analytical framework on the internal structure of consumption, this book explores how different categories of consumer spending interact and how these relationships shape the broader structure of consumption. The analyses focus on timely and policy-relevant issues, including the distributional impacts of the COVID-19 pandemic, inflation, the implementation of safe drinking water standards (with particular attention to low-income households), and the potential effects of carbon taxes on consumer expenditures. A key strength of the framework lies in its ability to derive comprehensive arrays of own- and cross-price elasticities from household expenditure survey data--even in the absence of direct price information.