Chart Controls III
This chart animates four dimensions of global development data—life expectancy, fertility rate, population, and time—using a bubble chart. Each circle represents a country, positioned by life expectancy and fertility rate, with size encoding population via a power scale. The animation steps through years, transitioning all circles simultaneously. A dropdown menu filters the display by region. The visualization is built with D3 v3, using `d3.scale.pow` for sizing, `d3.nest` to group data by year, and the `d3.timer` function to drive transitions. Data comes from the included `lfp_all.csv` file.