One of the main points in the report: Even though small businesses are (understandably) focusing most of their advertising on Google AdWords, there may be a bit of an untapped opportunity in Bing. AdWords advertisers through Pricing Engine saw an average clickthrough rate of 2.4 percent (compared to 2.3 percent on Bing), but the price for those clicks was lower on Bing, which saw a cost-per-click of $1.10 (versus $2.40 on AdWords). Pricing Engine also said stores were the biggest category in terms of number of accounts (17 percent of the total), while digital services firms were the biggest spender on AdWords, with an average monthly spend of $3,200 per month.