This visualization shows population over time by region, with multiple colored lines tracing each region’s trajectory from 1950 to 2100. The chart uses a time scale for the x-axis, a linear scale for population, and an ordinal color scale with a custom legend. D3’s `nest()` and `scaleOrdinal` group and color the series, while `d3.line` with `curveBasis` smooths the paths. Data comes from UN population estimates and medium-variant projections, melted into a tidy format for plotting as SVG.