Every two months Alexa's crawlers go out and scour the web bringing down 100 Terabytes of Web content and over 4 billion URLs into the archive. In the process we discover over 18 million unique sites on the Web. These are e-commerce sites, blogs, news sites and more. Virtually anything you can imagine is on the web spread out among these 18 million sites.
But how much traffic do these sites get? It depends on your Alexa Traffic Rank. Let's break it down by Alexa's Rankings, starting with the Top 500. Out of a total of 18 million sites to choose from, the Top 500 represent less than .003% of sites. But, as you would expect, these sites get a disproportionate amount of traffic. In fact they get 45% of all traffic. No, that's not a misprint. The odds that any Web surfer in the world is on a Top 500 site at any give time is about 50/50.
Moving down the rankings, if you take Alexa's Top 100,000 sites you'll find that almost 3 out every 4 clicks are spoken for. In other words, almost 75% of all the traffic on the web goes to the sites in the Top 100K list, leaving the remaining 18 million or so sites to fight over the scraps.
Like the distribution of wealth on the planet, the distribution of traffic on the Web is extremely lopsided. The Top 500 are champagne and caviar. Sites 501 - 100,000 are meat and potatoes. The rest are hungry.