This area chart visualizes world population by year up to 2015, using a smooth curve filled in maroon. The x-axis maps time via `d3.scaleTime`, while the y-axis uses `d3.scaleLinear` with tick formatting that abbreviates billions. Data is loaded from a CSV using `d3.csv`, and the path is generated with `d3.area()` and `curveBasis`. Axes and labels are built with `d3.axisBottom` and `d3.axisLeft`, rendered as SVG.