As I suggested previously perhaps the effect was more spread out this year because of the closeness of the last Friday before Christmas - the traditional defintion of 'black Friday' - to Christmas itself. Thus perhaps the previous nights were more busy than they would have been, particularly the previous Friday, but of course it's always difficult to tell, since the recession presumably hasn't helped overall, and if one night's extra work is spread over several other nights then it's often difficult to tell.
But these things change over time and there are always other factors to consider. For example, because it was on a Saturday evening and because of last year's awful weather I thought Christmas Eve might be better than last year, but it was dead as a dodo. But I think this is perhaps a longer term trend - Christmas Eve seems to have really dwindled over the years.
But perhaps the best response is not to spend too much time thinking about these things, since it ultimately gets you not very far
