The 20 most expensive keyword categories in Google AdWordsDespite its reputation as a search juggernaut, it’s no secret that Google is an advertising company at heart. In fact, 97 percent of Google’s revenue, which totaled $33.3 billion in the past twelve months, comes from advertising.

And most of that sum comes from AdWords, Google’s auction-based marketplace where advertisers bid on keywords to compete for top ad placement.

WordStream, a provider of hosted software and tools specially designed to optimize search engine marketing campaigns, conducted a research to discover which keyword categories get the highest costs-per-click in Google’s AdWords solution. WordStream compiled data from its own keyword database and from Google Keyword Tool to determine the top 10,000 most expensive English-language keywords over a 90-day period.

Subsequently, the list was organized into categories by theme. The largest keyword categories were then 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.

The top twenty keyword categories that fetch the highest costs-per-click are:

1. Insurance
2. Loans
3. Mortgage
4. Attorney
5. Credit
6. Lawyer
7. Donate
8. Degree
9. Hosting
10. Claim
11. Conference Call
12. Trading
13. Software
14. Recovery
15. Transfer
16. Gas/Electricity
17. Classes
18. Rehab
19. Treatment
20. Cord Blood

To present the results of their research, WordStream made this infographic:

Where Does Google Make Its Money? [ infographic ]