This visualization shows the economic and health progress of nations from 2000 to 2009, plotting income per capita against life expectancy for each country. Each circle represents a nation, with its size reflecting population and color indicating geographic region. The animation transitions through years automatically, with start and stop buttons controlling playback. The code uses d3.v2 with scales, axes, and a 30-second transition tween that interpolates yearly data from a JSON file, while enabling mouse interaction to scrub through years after the animation completes.