This chart displays population estimates and projections from 1950 to 2100 for regions worldwide, using multiple lines colored by country and sorted by their final population values. The visualization relies on d3.csv to load UN data, d3.nest to group rows by region, and d3.line with curveBasis to generate smooth paths. A custom colorLegend module renders the categorical color scale, while axes are built with d3.axisLeft and d3.axisBottom, and the data is reshaped through a custom “melting” process that converts wide-format year columns into long-format rows.