Mobility Rate Bubble Chart
This bubble chart displays the mobility rate and median parent household income for universities in California, sourced from the Opportunity Insights Mobility Report Cards dataset. Each circle's size is scaled by the average number of students per cohort using a square-root scale, while its color indicates the trend in the percentage of parents from the bottom income quintile, diverging from green to red. The visualization is rendered as an SVG using D3.js v5, and it employs `d3-scaleDiverging` and `d3-scaleSqrt` for color and size mapping. It includes axis labels, average lines, and a custom legend, and the data is filtered for California institutions.