Richard Skolnik, teaching Yale's Essentials of Global Health course on Coursera, explains how public health researchers measure the burden of disease worldwide. He introduces the Disability-Adjusted Life Year, or DALY, a metric that combines years of life lost to early death with years lived with disability into a single number for comparing health problems across countries and conditions. Skolnik walks through why simple mortality counts miss most of the picture, since chronic illness and disability can cost populations more healthy years than death itself. He connects the DALY to demographic patterns, showing how age structure, fertility, and mortality trends shape which diseases and risk factors matter most in a given country. The lecture sets up the rest of the course's sessions on specific causes of death and disability by giving students the tool used to rank and compare them. It is a plain, lecture-hall walkthrough with slides, aimed at students new to global health metrics.