A streamgraph displays changes in five data series from 1996 to 2018, including happiness scores, mood disorder diagnoses, and suicide-related metrics. Using d3.stack with stackOffsetSilhouette, the code layers filled areas symmetrically around a central axis, with d3.scaleOrdinal and d3.schemeDark2 assigning colors. The SVG rendering includes a gridline-based x-axis, and interactive hover effects dim other areas while tooltips identify the selected series. Data comes from a CSV file loaded via d3.csv.