Google is adding a bid adjustment in AdWords specifically for calls.
The bid adjustment for calls informs how often call information appears in mobile search ads.
From the announcement:
For example, if you’re a travel advertiser, you may see higher order values from calls because it can be easier to cross-sell rental cars, group tours and other vacation add-ons during a live conversation. Raise your call bid adjustments to show call extensions more frequently and drive more of these high-value call conversions.
The bid adjustment range is -90 percent to +900 percent.
Note, that this option is only available in campaigns created in the new AdWords interface, according to the help page, but that doesn’t appear to be the case. We’ve asked Google for clarification and will update here when we hear back. This is also listed as an “interaction” bid adjustment, so it looks like we will see more of these in the future, such as an interaction bid adjustment for location information.
Bid adjustments for calls is just the latest feature to roll out exclusively in the new AdWords experience.
Source: Search Engine Land