Projected 2030 economies can easily vary by plus 20% or minus 50% depending upon some country having a lot more problems or very good luck and policies. There is less margin of error for the developed countries like the US, Japan, and EuropeEven with those margin of error levels. China's economy should be the world's largest by a comfortable margin and possibly twice as big as the USA or India. (50-90 trillion)India and the USA and the EU-27 should be in the range of the same size in the next tier. (around 20-40 trillion)Japan, Germany, UK, France, Indonesia, Brazil, Russia, South Korea and Canada will be in the third level. (around 5-10 trillion)