This visualization compares population projections across four mobility scenarios—Default, Workshop, Shared, and Autonomous—using stacked bar charts. A dropdown menu switches between three pairwise comparisons, and each chart animates via `transition().duration()` to reflect the selected phase. The data, sourced from World Population Prospects 2017, is rendered as SVG using `d3.stack()`, `scaleLinear`, and `scaleBand`. Axes are generated with `axisBottom` and `axisLeft`, while `d3.format` customizes tick labels with abbreviations like "Mrd" for billions.