This line chart visualizes global population trends over time, grouped by world regions, using a multi-line layout with a categorical color legend. It combines historical estimates (1950–2014) with medium-variant projections (2015–2100) from UN population data. The visualization uses D3 v5 with `scaleTime`, `scaleLinear`, `scaleOrdinal`, `axisLeft`, `axisBottom`, `line`, `curveBasis`, and `nest` to structure and render the paths, while a custom `colorLegend` function displays the region labels as SVG circles and text.