The animated bubble chart above shows the evolution of carbon dioxide emissions across countries in the world from 1970 through 2010. The size (area) of the bubbles corresponds to the total emissions of a country. You can see how these bubbles move along two dimensions: the per-capita gross domestic product on the horizontal axis, and the economy's emission intensity along the vertical axis. Countries that grow affluent move to the right, and countries that become more efficient at reducing emissions move to the bottom. The axes in this diagram are logarithmic and span several orders of magnitude. The per-capita GDP axis starts from $100 per person and increases to $100,000 per person. This diagram is able to display four dimensions: the vertical and horizontal axes, the bubble size, and the movement over time. It is an example of how web technology can help better explain complex data patterns. What can you learn from the diagram? First, the bubbles are getting bigger over time, in particular the ones for China and India. Second, you can visualize a negative relationship between emission intensity and per-capita GDP. Countries that are getting richer tend to lower their emission intensity. The diagram was programmed in the web language SVG (scalable vector graphics) based on data from the World Bank's World Development Indicators.