Currently Adsense home page says there are 2 million+ AdSense publishers.
The World population is now 7 billion.
Internet users 2.405 billion. ( http://www.internetworldstats.com/stats.htm )
This gives 1200 internet users for one account. Can they give reasonable income?
Average American internet user is spending 8 to 10 hours per day online. 80% is spent in mail, facebbook, Twitter and Search. Only 20% is spent for content reading for leisure. May be it means, 80% of the time is spent for business reasons or business related transactions and only 20% is spent for leisure transctions. During leisure time he may visit about 15 pages. The pages may contain 2 to 3 ads per page. ATKearney estimates that it will translate to 6 cents per users at $1.80 per 1000 ad impressions.
This means that average site can have 7200 cents per day, which is 72 dollars per day. It is plausible if 1200 visitors are visiting 18,000 pages a day. Or it can be interpreted that on an average the adsense publishers can have 18,000 page views per day. Interesting number.
Trillion web pages indexed by Google in 2008
Montly unique visitors to US Retail sites
Internet users visits average 2,645 pages in a month