Str82u - 3:59 pm on Dec 22, 2012 (gmt 0)

@Sgt_Kickaxe - right, that's why I wrote

, but with Google devaluing some exact match terms in links and titles it's likely that it is the results of the "Home" links passing more authority to the home page

Internal pages don't neccessarily have to have a link named "home", some sites have img links to the homepages, but in general my assumption was nothing with sitelinks had changed and the links to the homepage were likely generic text or image which may have somehow gained value over the years worth of SE algo changes.

Sorry I wasn't more clear.

The description "end of year ranking review" doesn't express when this happened exactly or if it was a gradual process. "Trend" might not be a trend but an specific cause sometime during the year.