Ah! I thought it had something to do with holidays...
Also, on the US graph there's also a discernable a mini-spike right on or just before the first quarter. I can't come up with an answer for that. One guess is that people are looking into planting flowers for the springtime around then.
Damn! I thought about Mother's Day and Valentine's Day, but I searched for those phrases, I didn't try to think of what they have in common. I also noticed the small spike near Christmas.
Thanks for preventing me from having this going on in the back of my head all day.
Looks like something to do with taxes, but I can't figure out the phrase that matches his trends. "Taxes", "income tax" and "tax forms" all produce trends that have similar peaks as his, but nothing has that distinctive rise and dip at the end of the year.
Neat idea. This seems like the sort of thing that could be done with genetic algorithms - the problem has a natural objective criteria and evolving a search string is relatively straightforward.
First guess was football, since it would be seasonally periodic, and would spike in different times of the year due to the different international seasons... but the peaks aren't in the right spot, so no dice =(
Flowers are sent in the highest volumes on Valentines day and Mother's day.
Both graphs have spikes in February. In Britian, Mother's day is in March. In the US it is in May. These correspond directly to the spikes presented.