In a sign that viewers are growing more interested in watching television shows on their computers, Nielsen will begin measuring TV viewing on computers by the end of the year in its people metre household panels, the company said.

The effort is part of a broader plan to measure television viewing on mobile devices such as iPods and phones, according to the audience measurement company.

The announcement is part of an update of Nielsen's anytime/anywhere media measurement initiative, called A2/M2. Nielsen first announced its plans to integrate TV-based and internet-based television viewing in October 2006.

"Clients have told us that 'following the video' as it moves to computer screens must be one of our top priorities," Nielsen said in the update. However, Nielsen said customers also want to ensure that the Internet measurement system doesn't interfere with the quality of the traditional television ratings system.

In order to give its clients what they want, Nielsen is creating a new Nielsen TV/Internet Convergence Panel to measure television and internet viewing in the same households.

The plan has its challenges, the company said. For instance, more than half of the 98 eligible households declined to participate in the new program, citing privacy concerns. Only 44 households agreed to take part in the new measurement system, Nielsen said.

"Refusing households told us that although they trusted Nielsen to maintain their confidentiality with television measurement, they felt computer data is more personal and personally identifiable than television data," Nielsen said. The company said it would do more research to find ways to overcome panelists' concerns about their privacy.

Nielsen said it expected to begin the phased test of the new program by the third or fourth quarter of this year. If all goes well, Nielsen will expand the program, but if there are problems, the company will suspend it.

"Measuring television over the computer is the first in a series of building blocks that will give us a full picture of online television activity," the company said. "We believe that by making computer measurement optional and measuring only online television programming as a first step, we can maximize the number of panelists willing to participate while minimizing the impact on sample quality."

Nielsen said it is also developing ways to measure television viewing on phones, MP3 players and other mobile devices. The company said it is working with developers at LG Electronics and Harris to develop a measurement system for digital television on mobile devices.

Nielsen is also working on phasing out its paper-based measurement system and replacing it with an electronic one.