According to search marketing firm Efficient Frontier, Google gets over three quarters of all search engine marketing (SEM) dollars, reports ClickZ.

The firm examined purchases it made on behalf of clients from Q4 of 2006 to Q4 of 2007. It found Google's share of SEM spend jumped from 71 percent to 77 percent in that time.

Despite the debut of Panama, Yahoo earned less and saw spending drop by six percent in that time period, falling from 24 percent of total dollars spent to 18 percent.

MSN led the pack in ROI, with results 27 percent higher than average. That's attributed to the smaller footprint it has in the market. Yahoo's ROI rose by 40 percent despite, or perhaps because of, the drop in spending.

Overall, advertisers increased their search engine spending by 29 percent, said Efficient Frontier.