D3 Data Visualisation for biggest companies in the world by market capitalization

Check out the tutorial on how to build this page, with references for the data used.
Radius of a pie chart represent a total value of the companies in this stock exchange included in this calculation, proportional to other stock exchanges.
Some additonal info:

• Use middle mouse button to zoom in and out. Left click and hold to move while zoomed in.
• Hover over specific circle for more details in tooltips.
• On blank area right of the map use middle mouse button to scroll up and down the page; legend is shown on the bottom of the page.