Search marketing software provider WordStream has released data showing the top 20 high-volume keyword categories with the highest costs-per-click at Google. According to WordStream, the top five keyword categories are Insurance, Loans, Mortgage, Attorney and Credit (see the infographic below for more). Advertising accounts for approximately 97% of Google’s revenue. The keyword categories with the highest volumes and costs represent businesses with very high lifetime customer value – in other words, these industries can afford to pay lot to acquire a new customer. These businesses include lawsuits, mortgage applications, and server hosting. Some high-volume keyword categories have lower CPCs because advertisers have slimmer margins to expend on PPC advertising. WordStream compiled data from its keyword database and the Google Keyword Tool to determine the top 10,000 most expensive English-language keywords over a 90-day period. This keyword list was then organized into categories by theme. The largest keyword categories were determined by weighting the number of keywords within each category, as well as the estimated monthly search volume and average cost per click for each keyword.