NEW YORK, February 3, 2005 - Arbitron Inc. (NYSE: ARB) and comScore Media Metrix, a division of comScore Networks, Inc., announced today that the Monday - Sunday 6AM-Midnight audience for the three measured networks increased 16 percent from an estimated 4.2 million people per week, age 12 and older, in November 2004 to almost 4.9 million for the December 2004 survey period.

The midday daypart of Monday-Friday 10AM-3PM is the heart of the working day. Listening to the online radio networks measured by comScore/Arbitron peaks during midday, with 655,000 people age 12 and older listening during an Average Quarter-Hour Monday-Friday 10am-3pm. Average Quarter-Hour (AQH) is the estimated number of people who listen during an average 15-minute period of time during a given daypart. 

The December report of the comScore Arbitron Online Radio Ratings service rated the three charter subscribers-America Online's AOL^® Radio Network; Yahoo!^®'s LAUNCHcast; and Microsoft's MSN Radio and WindowsMedia.com-during an average broadcast week in the month of December. 

Persons 12+

Average Weekly Audience

December 2004

Geography: United States (50 states)

Note: Cume is defined as the number of different people who listen during a given daypart. Cume audience estimates for individual networks should not be added, because people who listen to more than one network will be counted twice. The reported audience for the total of the three networks is an unduplicated estimate of the number of different people who listened to one or more of the networks for a minimum of five minutes during the week.

The comScore Arbitron Online Radio Ratings service is based on a subset of approximately 200,000 U.S. participants within the comScore global consumer panel. Using proprietary and patent-pending technology, comScore passively and continuously captures the online behavior of these panelists, including online radio listening behavior. Subscribers receive Average Quarter-Hour and Cume audience estimates for 38 demographics and 15 standard broadcast dayparts. Each month, Arbitron will publish the average weekly audience for Persons 12+, Monday through Friday 6AM-7PM and Monday through Sunday 6AM-Midnight on its Web site (www.arbitron.com).

Arbitron represents the comScore Arbitron Online Radio Ratings service. For more information contact Diane Williams (diane.williams@arbitron.com) or Bill Rose (bill.rose@arbitron.com).

About Arbitron

Arbitron Inc. (NYSE: ARB) is an international media and marketing research firm serving radio broadcasters, cable companies, advertisers, advertising agencies and outdoor advertising companies in the United States, Mexico and Europe. Arbitron's core businesses are measuring network and local market radio audiences across the United States; surveying the retail, media and product patterns of local market consumers; and providing application software used for analyzing media audience and marketing information data. The Company has also developed the Portable People Meter (PPM^SM), a new technology for media and marketing research.

Arbitron's marketing and business units are supported by its research and technology organization, located in Columbia, Maryland. Arbitron has approximately 1,700 employees; its executive offices are located in New York City.

Through its Scarborough Research joint venture with VNU, Inc., Arbitron also provides media and marketing research services to the broadcast television, magazine, newspaper and online industries.

About comScore Media Metrix

comScore Media Metrix, a division of comScore Networks, provides industry-leading Internet audience measurement services that report-with unmatched accuracy-details of online media usage, visitor demographics and online buying power for the home, work and university audiences across local U.S. markets and across the globe. comScore Media Metrix continues the tradition of quality and innovation established by its Media Metrix syndicated Internet ratings-long recognized as the currency in online media measurement among financial analysts, advertising agencies, publishers and marketers-while drawing upon comScore's advanced technologies to address important new industry requirements. All comScore Media Metrix syndicated ratings are based on industry-sanctioned sampling methodologies.