Richard Skolnik, lecturer for Yale's Essentials of Global Health course, examines why health outcomes differ so sharply across and within countries. He walks through the major measures used to track disparities, including income, education, gender, and geography, and shows how these factors compound to shape who gets sick, who receives care, and who dies preventably. The lecture draws on global health statistics to illustrate gaps between wealthy and low-income nations, and within countries between urban and rural populations or different social classes. Skolnik connects these patterns to broader themes in the course, such as maternal and child health, nutrition, and access to immunization, arguing that disparities are not incidental but structural features of how health systems and economies are organized. The tone stays practical and data-driven rather than polemical, aimed at students building a working knowledge of global health policy. It is one session within a longer Coursera-linked lecture series on the essentials of the field.