This interactive bubble chart explores the relationship between population, urban population, and median age across various countries and years. Each circle’s x-coordinate maps to total population, its y-coordinate to urban population, with bubble size reflecting median age and color encoding the year of the data. Built with D3 v7, it employs `d3.scaleLinear` for continuous axes and bubble sizing, `d3.scaleOrdinal` with `d3.schemeCategory10` for categorical year colors, and uses `d3.axisBottom` and `d3.axisLeft` for axes. Hovering reveals a tooltip with the country’s exact statistics, while a legend identifies the color-year mapping. Data comes from the included `bubblechart.csv` file.