Business Models

Advertising Data Resources

Data about overall advertising industry, likely will include comparison forecasts.

World Advertising Research Center

Data from the IAB specific to online advertising. Includes yearly revenue chart going back to 2001.

IAB Insights

Data from Advertising Age, including annual reports and analysis of advertising spending

Ad Age Data Center

Answered question from “Google Answers” about advertising industry revenue (from 2003 but sources may still be relevant)

Google Answers