This visualization shows health expenditure and life expectancy across multiple countries from 1970 to 2007, using a horizontal stacked bar chart where each bar represents a country and segments show annual spending contributions. The chart uses D3 v7’s `d3.stack()` to create the stacked layout and `d3.scaleBand()` for country positioning, with years mapped to colors via `d3.scaleOrdinal()`. Hovering over any segment triggers mouseover and mousemove events that display a tooltip with the exact spending value for that country-year combination. The data comes from a CSV file loaded using `d3.csv()`.