One of our favorite and most useful posts from last year was an in-depth look at cost-per-click behavior during the 2006 holiday season by none other than Google's Chief Economist, Hal Varian. In the post Hal explained how CPC's and CPA's (cost-per-actions) vary over time to affect advertisers' ROI.

This year we have two new posts about CPC's and holiday trends over at the newly launched Google Retail Advertising Blog, a great source of information tailored to the needs of retail advertisers. The first post is Hal's updated look at the new data from the 2007 holiday season. The second has some tips regarding scheduling and consumer behavior specifically for your campaigns this winter. Remember, it's never too early to start your holiday planning.