Pay per click search engines are growing increasingly complex in their offerings. To help large advertisers cope with the increasing sophistication and complexity of these offerings some search engines and third party software developers have created software which makes it easier to control your ad spend. Some of the more advanced tools can integrate with your analytics programs and help you focus on conversion, ROI, and earnings elasticity instead of just looking at cost per click.
If you want to program internal bid management software you can get a developer token to use the Google AdWords API.
A few popular bid management tools are
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