If Google was an Internet Service Provider (ISP), it would be the second largest in the world. Of course, Google accounts for a large percentage of the largest ISP's traffic as well. The dataset includes all of Google's properties, meaning it encompasses the video giant YouTube as well. The chart below shows Google's share of all worldwide traffic and its growth since the beginning of 2007 (Arbor Networks gets its data from over 110 ISPs from around the world):
Google's share grows even larger (to as much as 8 to 12 percent) if you include estimates of traffic offloaded by the increasingly common Google Global Cache (GGC) deployments and if you account for error due to the extremely high degree of Google edge peering in consumer networks. Google now has direct peering (not transit) with more than 70 percent of all providers around the world (an increase of 5 to 10 percent from last year), which means that traffic from Google websites has a direct path to the ISPs.