Mobility Rate Bubble Chart
This bubble chart visualizes the relationship between median parent household income and mobility rate for universities in California, with circle size representing average student cohort count and color indicating the trend in parents from the bottom 20% of income distribution. Built with D3.js v5 and Vue, the SVG rendering uses d3-legend for color and circle legends, computes average reference lines with d3.mean, and draws labeled circles for selected universities. Data comes from the Opportunity Insights Mobility Report Cards dataset, filtered to include only California institutions.