Demographic history is the study of changes in the size, structure, and distribution of human populations over time. This field of research examines factors such as birth rates, death rates, migration patterns, and population growth to understand how populations have evolved and been shaped by various social, economic, and environmental factors. Researchers in demographic history use a combination of historical records, statistical analysis, and mathematical models to track and analyze changes in population dynamics, helping to uncover patterns and trends that contribute to our understanding of human history and society.