NEW YORK: Online tracking levels are rising rapidly in the US, as increasing numbers of companies vie to gather data covering consumers' internet behaviour, a study has discovered.

Krux Digital, the data management group, assessed 50 of the most popular US websites that did not require users to log in upon arrival, analysing between six and ten pages on each property.

The typical visit to a featured site led to the activation of 56 data collection processes, a total which can be compared with ten in 2010.

More specifically, the report revealed 300 monitoring firms currently gather online user data, a lift from 167 in 2010. Previous research by the Wall Street Journal pegged this figure at 131 two years ago.

Relevant operators here include ad networks, servers and exchanges, measurement organisations, demand side platforms allowing brands to manage campaigns, widgets and yield optimisers.

During more than half of visits monitored by Krux Digital, the triggering of tracking tools embedded on websites resulted in the launch of several similar systems directly linked to these services without being embedded.

This stems from advertising firms attempting to add such software to websites in an effort to generate the statistics necessary to sell ads in auctions.

Gordon McLeod, the president of Krux Digital, told the Wall Street Journal that this had essentially left publishers in the unusual position of not knowing how much material is being collected.

"It may be the first medium where the buyers have more information about the price, the value and the amount of inventory than the seller," he said.

A major contributor to this trend, according to Krux Digital, is the rise of real-time bidding exchanges, where online systems automatically bid for individual website visits in auctions.

Forrester, the insights provider, suggested that real-time bidding made up 13% of the display advertising category last year, a share which is set to hit 18% in 2012.

"It's gone from virtually zero in 2009 to about a fifth of the entire market right now," Michael Greene, a senior analyst at Forrester, said. "We've moved from a traditional advertising model of buying 1,000 impressions. Now you evaluate and buy a single impression."

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