This map was produced by Angelo Di Donato (@outofbabylon) using d3.js , cartogram.js and Python to get and clean the data from The World Bank. It was inspired by the out of date map over at worldmapper.org. Unfortunately, not much has changed. Due to differences in the implementations, the two maps cannot be directly compared to one another.
The code (including most of this page) was adapted from the example provided by shawnbot. You can see the source code over on Angelo's github.