Mobility Rate Bubble Chart
This bubble chart displays the mobility rate of California universities, plotting median parent household income against the percentage of students who move from the bottom to the top income quintile. Circle size encodes the average student cohort, while color shows the trend of parents in the bottom 20% of income over time. The visualization uses D3.js v5 with d3-legend, SVG rendering, and data from Opportunity Insights. Background median lines and labeled circles for select universities add context, with axes and legends generated through D3 scales and SVG elements.