As director of paid search at Greenlane Marketing, a web marketing firm based in Eagleville, Pennsylvania, Christian Wenzel spends a lot of time studying who's clicking on his clients’ Google ads. He’ll look at things like where they're located to see if, for instance, people in Pennsylvania are more likely to click on a given ad than people in California. Then, he'll tweak the ad campaign accordingly in hopes of maximizing its effectiveness.

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