This bubble chart visualizes the relationship between healthcare spending (USD) and life expectancy across several countries from 1970 to 1974. Each bubble represents a country-year observation, with bubble size encoding the year and color distinguishing countries. Hovering over a bubble reveals a tooltip with exact values. The chart uses d3.v7's scaleLinear for axes and bubble sizing, scaleOrdinal for coloring, and SVG circles with transition-based tooltip interactions. Data is loaded from a local CSV file.