According to Marchex’ 2015 Click-To-Call Commerce Mobile Performance Report, click-to-call has emerged as the most common form of purchase-oriented activity from mobile ads. They report that click-to-call commerce, in which a consumer makes a phone call from a mobile Web page or app and makes a reservation, appointment or purchase, will exceed $1 trillion this year.

In its most recent white paper, Marchex set out to determine whether display ads are influential in driving consumers to make purchase-oriented calls. According to The Missing 98%: Why Display Advertising Isn’t Getting the Credit It Deserves, “The advertising technology ecosystem has historically focused on tying display ad exposure to e-commerce purchases, or other online actions such as filling out a lead form or visiting a product web page. However, for most advertisers, the goal of a display advertising campaign is offline, such as an inbound phone call or in-store purchase.”

According to the report:

Not much click-to-call activity occurs directly from display advertising units.
Whereas a paid search campaign that uses call extensions may see call-through rates as high as 20%, Marchex research has shown that it can take an average of 500,000 impressions from a display ad with click-to-call functionality to generate a quality phone call.

But display advertising does influence consumers to make a phone call in the future.
Data from beta customers of Marchex Display Analytics shows that it can take an average of 8,000 impressions from a display ad to influence a phone call within 2 weeks. In other words, display ads influence 60 times more phone calls than they do a direct click-to-call. On average, they found that approximately 2% of phone calls occur directly from display ads or landing pages, and the rest occur in the days or weeks following exposure.

Marchex identified three major challenges of view-through attribution for phone calls:

1. Lack of a common identifier across online and offline
2. Cross-screen attribution
3. Latency

The white paper outlines these challenges in greater detail and makes suggestions on how to address them.