This visualization displays population over time by region, with a multi-line chart that sorts regions by their final population values. The data is melted from wide-format United Nations CSV files into tidy long-form rows using a custom function that iterates over years. The code uses d3.csv, d3.nest, d3.scaleTime, d3.scaleLinear, d3.scaleOrdinal, d3.line with curveBasis, and a custom color legend module. Animated axis labels and a title are rendered as SVG elements.