Businesses receive nearly 34 billion inbound calls each year from mobile search alone, according to the following Invoca infographic. "Yet most search marketers continue to invest their PPC budgets to drive online conversions and form-fills," Invoca states.

Are you missing out on those prime opportunities to convert inbound callers? The tips in the infographic can help.

First, make sure to cover the basics, such as putting your phone number on ads and landing pages. Then track all those calls, and measure the value and outcome of each call.

"Gather in-depth call analysis," recommends Invoca. "Integrate call data with your bid management, analytics, CRM, and retargeting tools."