Insurance-related keywords are the source of 24% of Google’s AdWords revenue, with the highest CPC coming in at a whopping $54.91, according to a study by search marketing company WordStream. The company used its own keyword database and the Google Keyword Tool to come up with the top 10,000 most expensive English-language keywords over a 90-day period.

Examples of key phrases in the Insurance category included “buy car insurance online” and “auto insurance price quotes.”

Next in line came the Loans category, commanding 12.8% of revenue with CPCs as high as $44.28. Typical keywords in Loans include “consolidate graduate student loans,” and “fixed home equity loan rates.” Third was the “Mortgage” category, which, one supposes, could have been put together with Loans. As its own category, Mortgages represented 9% of revenue, with the highest CPM coming in at $47.12.

Rounding out the top 10 categories, in order of percentage of revenue represented, include Attorney, Credit, Lawyer, Donate, Degree, Hosting and Claim. Again, Attorney and Lawyer could be argued to be a single category, but WordStream broke them into two separate buckets.

Clearly, the categories representing the highest revenue potential for Google — with both high CPCs and high volume — are those with large potential customer bases wiling to pay the most to acquire a customer. These are advertisers for whom acquiring a customer represents a substantial reward, either because it is an expensive purchase or because the customer has a high lifetime value.

Here’s the full top 20 with the highest search volume and CPC, via WordStream:

Insurance (example keywords in this category include “buy car insurance online” and “auto insurance price quotes”) Loans (example keywords include “consolidate graduate student loans” and “cheapest homeowner loans”) Mortgage (example keywords include “refinanced second mortgages” and “remortgage with bad credit”) Attorney (example keywords include “personal injury attorney” and “dui defense attorney”) Credit (example keywords include “home equity line of credit” and “bad credit home buyer”) Lawyer (“personal injury lawyer,” “criminal defense lawyer) Donate (“car donation centers,” “donating a used car”) Degree (“criminal justice degrees online,” “psychology bachelors degree online”) Hosting (“hosting ms exchange,” “managed web hosting solution”) Claim (“personal injury claim,” “accident claims no win no fee”) Conference Call (“best conference call service,” “conference calls toll free”) Trading (“cheap online trading,” “stock trades online”) Software (“crm software programs,” “help desk software cheap”) Recovery (“raid server data recovery,” “hard drive recovery laptop”) Transfer (“zero apr balance transfer,” “credit card balance transfer zero interest”) Gas/Electricity (“business electricity price comparison,” “switch gas and electricity suppliers”) Classes (“criminal justice online classes,” “online classes business administration”) Rehab (“alcohol rehab centers,” “crack rehab centers”) Treatment (“mesothelioma treatment options,” “drug treatment centers”) Cord Blood (“cordblood bank,” “store umbilical cord blood”)

Here’s WordStream’s infographic summarizing its data:

