A stacked bar chart displays gender distribution across Chinese provinces, with male and female counts stacked per province. Users toggle between raw counts and percentages of total illness via radio buttons, triggering animated transitions that rescale the y-axis and re-stack the bars. The visualization uses D3.js version 3.5.6 with the `d3.layout.stack` API, ordinal and linear scales, SVG axes, and transition methods. Data comes from two CSV files, though only `data3.csv` containing provincial gender counts drives this chart. Hovering highlights bars through CSS opacity changes.