Prompted by recent headlines about declines in Facebook market share and Google's sponsored clicks, a couple of blog posts by Hitwise analysts Heather Dougherty and Bill Tancer examine the sites' traffic data, writes MarketingCharts.

Facebook Traffic

Facebook has grown considerably in the last two years, with market share of visits having reached the highest point in the week ended Dec. 29, 200. But two months later, visits are down 27 percent from the peak, according to Dougherty.

She ascribes the decline in part to the shift toward older demographics (which spend less time online) and college school-year seasonality — students are away at school — with spikes in Facebook traffic during the Thanksgiving and Christmas holidays, when they're back home.

Nevertheless, average time spent on Facebook continues to increase unabated, according to Hitwise data. It stands at 21 minutes, 22 seconds (for the week ended Feb. 23) — 73 percent more than a year earlier.

Google Traffic

With reports that Google's paid search clicks down in January, there should be a drop in the amount of traffic from Google to retail sites, says Hitwise's Tancer, who points out, however, that percentage of such traffic has been increasing:

"If we focus in on daily data (year-over-year comparison) we see that Google traffic to retail is also up on a daily basis when we compare January/February 2007 with 2008," he adds.