The transaction is valued at $71.2 million.
Jupiter, the market leader in the category, has foundered under the pressure of being a stand-alone public company, and its market cap at the end of trading today was $22.4 million. It has also had several rounds of layoffs, the most recent occurring earlier this month when one-third of its staff of 600 was let go.
NetRatings also announced it was purchasing the more than 80% of ACNielsen international property eRatings.com it didn't already own. That deal is valued at $16.4 million.
NetRatings, which came to the market later than Jupiter, has nonetheless benefited from its association with VNU, which owns its stake via the ACNielsen and Nielsen Media Research units. Its market cap at today's close was $432.7 million.
NetRatings said that as a result of the merger, it would increase its number of clients by 94%.
A number of management changes were also announced. NetRatings said Bill Pulver, formerly president of ACNielsen eRatings, will become president-chief operating officer of NetRatings. Dave Toth will remain as chief executive officer until the deal closes, at which time Mr. Pulver will become CEO.