The Internet began as a communication tool but has transformed into a universal technology supporting virtually all sectors across the economy, much in the same way as electricity and water networks. Given the importance of the Internet, there is a high level of interest in being able to measure the Internet economy as a way to understand the effects of various investment strategies, regulatory rulings and policy decisions. This report examines and categorises various approaches for measuring the Internet economy. It also introduces a methodology for measuring value added from Internet-related activities, and finds that at least 3.2% and up to 13.8% of business sector value added in the United States in 2011 could be attributed to Internet-related activities, depending on the scope of the definition. Data from 2010 and 2011 show that these percentages are growing over time, highlighting the increasing importance of the Internet in the overall economy.