very interesting cyclic pattern

happen to see a stat called google domestic trend. it's basically an index tracking ppl's interest in certain topics by calculating the number of related queries. interestingly, you can find a very obvious cyclic pattern for most of the trends it tracks. generally, the pattern is repeated annually and will have a peak at some specific time during a year. and most have their peaks around year end.

Automotive:

http://www.google.com/finance?q=GOOGLEINDEX_US:AUTO

Luxury goods:

http://www.google.com/finance?q=GOOGLEINDEX_US:LUXURY