There are times when it’s clearly far quicker to call with a question than it is to find an email address, compose a message, and then wait for a response. Or tap out a text. Or find someone who’s actually online for a chat exchange. These are all communications channels that most businesses would rather push customers or customer prospects to use.

Yes, it’s far more common to leave out phone numbers or voice contacts on websites than one would expect. That’s a big oversight in any digital marketing strategy: one that could be costing businesses real leads.

Concrete evidence comes from a recent analysis by Invoca, a software company from Santa Barbara, California, that sells a call intelligence platform used by marketing teams. Here’s the stat you care about the most: more than half of the 32 million calls analyzed by the company were driven by mobile marketing activities.

Now, correlate that with the all-too-common for businesses to leave out voice contacts on websites.

Mind you, Invoca is in the business of call intelligence, so it’s not surprising that the company would come up with a conclusion that talks up the value of tracking voice leads or interactions. But its data makes a lot of sense. Here’s the observation from Invoca President Eric Holmen:

“We know that phone conversations are important, but we wanted to really dig into our data to determine what actions motivate inbound calls to businesses and how those conversations impact businesses on the other end of the line. Our data shows that industries emphasizing the call channel and making it easy for their customers to move seamlessly from digital to voice interactions will come out substantially ahead.”

Invoca’s technology, called the Invoca Call Intelligence Platform, provides a view into which marketing channels are driving specific lead activity. Simply put, you can track calls just like you would clicks. The software integrates with pretty much any customer relationship management system, call center platform or marketing automation application you can think of including Adobe, Doubleclick, Google AdWords, HubSpot, Microsoft Dynamics, and Salesforce.

Home security company Vivint uses Invoca’s technology to gather metrics such as which page an inbound caller just visited on its website, the words he or she used in searching for information, or their specific geographic location.

“This has been a critical component of our marketing stack. … It helps us understand the data behind the people who are calling us,” said Jason Owen, vice president of marketing. “We also know that they are more likely to convert [into a customer] than someone filling out a web form.”

Over the next three years, the imperative to prioritize better call intelligence will grow far stronger. Research firm BIA/Kelsey projects that calls to businesses made via mobile phones will reach 162 billion annually by 2019, more than double last year’s volume. “Mobile users have a purchasing intent,” said analyst Abid Chaudhry. “Not only are they high in volume, they are likely to complete a transaction. That puts a mandate on the marketing organization to make sure that a call converts.”

Along with Invoca, another fast-growing player in this category is Chicago-based DialogTech, which counts companies like Uber, Zendesk and Terminix among its customers. In late June, DialogTech launched a service that attributes specific keyword data with activity related to Google call extensions.

“Voice has been treated as the Rodney Dangerfield of technology,” said the company’s founder and CEO, Irv Shapiro. “Self service channels. Apps. Some businesses will do pretty much everything they can not to talk to their customers.” (DialogTech’s former name was Ifbyphone.)

Increasingly, more consumers are responding with this message Shapiro said: “If you will not talk to me, I will find someone who will.”

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