Consider the following series of graphs, each showing the trend for various terms in the New York area during the last five Decembers. The terms are "chinese", "italian", "sushi", and "steak". (You can click each image to zoom in.)
First, 2008:
2007:
2006:
2005:
And finally 2004:
Pretty boring, right? A bunch of lines tracking sideways. No seasonalities, no weekend effects, no pattern whatsoever.
With one exception.
Every December 25th, the blue line (representing searches for "chinese") ticks sharply upward before returning to its normal level the next day. None of the other lines exhibit that bump. Even though these trends aren't filtered for food-specific searches, that is the clear fingerprint of a time-honored love affair (even inspiring an academic paper [pdf] on the phenomenon).
Let's not be shy, we all know what that spike is: Jews looking for Chinese food on Christmas. It's American as apple pie.
A live view of this trend is available for each year: 2008, 2007, 2006, 2005 and 2004.