NEW YORK: Nielsen, the research firm, is reportedly partnering with websites including Facebook to develop a new metric for measuring online ad effectiveness.

The Wall Street Journal reports that the research firm will combine data provided by online partners with representative panel data to develop a Gross Rating Points (GRP) score for individual ads.

Nielsen already measures and publishes TV ratings for US networks.

The online audience data - consisting of details such as age group and gender - is anonymous.

Other organisations involved in the Nielsen project - which is still in the testing stage - are said to include Procter & Gamble and several large media firms.

Ad agencies and publishers stand to benefit from the widespread adoption of GRP metrics.

Accurate measuring of an ad's audience would give advertisers a much more precise way of monitoring its effectiveness.

This would, in time, make online media pricing much more efficient.

Currently, media buyers have to base their decisions on cruder measures such as site traffic and click frequency rates.

The Global Media Intelligence Report, released by eMarketer and Starcom MediaVest Group earlier this month, suggests that online made up 14% of total adspend in North America in 2009.

By 2014, this proportion is forecast to reach 21%.

Data sourced from Wall Street Journal; additional content by Warc staff