Mortgage-related search tems dropped in price by 30 percent, leading an overall decrease in average keyword prices of 15 percent from April to May, to an average of $1.66 from $1.95, according to the Fathom Online Keyword Price Index, released today.

This fall comes after an increase of 11 percent in keyword prices from March to April, led by mortgage spiking with a 20 percent increase. The keyword prices of the monitored categories prices fell across the board, except for automotive terms, which increased by 7 percent to $1.50.

The largest category price drops were mortgage, which plummeted 30 percent to $4.52, and investing, which fell 11 percent to $1.81. The drop in mortgage-related keyword prices heavily weighted the overall average drop--without including the mortgage-related keywords, the decrease in overall keyword price was 3.29 percent, a Fathom spokesperson said.

Consumer services, broadband telecommunications, and wireless telecommunications search terms all held their losses below 5 percent, with consumer services falling 3 percent to $1.09, broadband terms falling 3 percent to $2.02, and wireless falling only 1 percent to $1.00.

Retail and travel and hospitality terms both fell 6 percent, with retail closing the month at 49 cents and travel at 87 cents.

According to Fathom's senior vice president for channel management and marketing, Gregg Stewart, keyword price watchers would be mistaken to predict a trend based on a one-month decrease.

"Given the fact that as you look at this over time, you'd have to look at more than a one-month event to have a trend. We've seen this sort of short-term volatility before," Stewart said, citing the nearly across-the-board decreases from December to February.

Stewart said that the decrease could be due to a sudden increase in inventory, or it could be the result of the beginning of an end-of-quarter slump.