This example visualizes population over time by region, showing six major world regions as distinct colored lines from 1950 to 2100. The chart uses a line generator with curveBasis for smooth paths, while a color legend identifies each region. The code melts wide-format UN population data into tidy rows, combining estimates and medium-variant projections from CSV files. It employs d3.scaleTime, d3.scaleLinear, d3.scaleOrdinal, d3.nest, and d3.axisBottom/axisLeft, rendering as SVG with custom tick formatting for abbreviated population values.