• by Tameka Kee , August 31, 2007

New Nielsen//NetRatings data on month-over-month user retention for the Web leaders in search, career development, and travel found that sites like Google, CareerBuilder and Expedia could consistently keep the same users coming back.

But keeping those users from spending time with the competition is more difficult--as at least a third of all surfers in each category still visited a competitor's site.

With search, for example, Google led with a retention rate of 79%, followed by Yahoo's 69%, and MSN/Windows Live at 65%.

But while a majority of users returned to search again, they also chose to search with another engine.

MSN had the highest level of overlap, with 84% of users searching elsewhere, while 78% of Yahoo's searchers did. Google searchers were the most loyal, although well over half (63%) still crossed over to the other engines.

According to Ken Cassar, Nielsen//NetRatings chief analyst, the sheer volume of available resources on the Web makes it hard even for market share leaders to maintain a competitive advantage.

"Even Web sites with established and loyal audiences have to continually innovate to stay ahead," Cassar said. "Google stepped into a highly competitive market when it first launched, and armed with a better mousetrap, it quickly became the company to beat. Given the high degree of competitive sampling in the search business, it is conceivable that it could happen again."

Whether it means that innovative competitors like Ask and newcomers like Spock or Hakia really have a shot at Google's top spot remains up for debate, as industry analysts like Silicon Alley's Peter Kafka argue that the Nielsen data only shows "how habitual big three searchers are, even when another engine reportedly has a better mousetrap."

Advertisers, however, may benefit from a diversified paid search strategy--as the overlap data shows that there are impressions (and a boost in frequency) to be gained from all three engines.

Among the three categories, the search leaders came out on top in terms of repeat visitors--retaining an average of 71% of users who searched from their home computer. Cassar noted that search is "a daily online activity for most Web users," so it's not surprising that they displayed such a high level of retention.

With career and travel sites, however, visits are often pegged to specific life events, and as such, their overall retention rates were much lower.

The leading career sites retained an average of 38% of visitors, while travel sites retained just 31%. Cassar added: "Career development and travel sites are used less frequently, so their challenge is to be top of mind when it comes time to look for a new career opportunity or plan a trip."