Mobility Rate Bubble Chart
This visualization shows the mobility rate of California universities, plotting median parent household income against the percentage of students who rise from the bottom to the top income quintile. Circle size encodes average cohort size, while color represents the trend in parents from the bottom income bracket. Built with D3 v5 and Vue, it uses `d3.scaleSqrt` for radius, `d3.scaleDiverging` for color, and `d3-legend` for legends. Data is filtered from Opportunity Insights' Mobility Report Cards CSV and rendered as SVG with average reference lines.