New data from research undertaken by voice-centric marketing technology business, ResponseTap, shows that smartphones convert three times as many sales as previously thought.

The call tracking and analytics company said the discrepancy has arisen because most brands only track sales conversions when they take place within the smartphone browser. Whereas in reality, many consumers research brands on a mobile device but then call to purchase.

The data, which was based on an analysis of more than 450,000 on and offline transactions, shows that on average 0.4% of smartphone browsing results in a transaction. But when you include transactions made via a phone call, this figure jumps to 1.3% – over three times higher.

The graphic below shows how conversion rates on other devices are similarly impacted by adding in phone sales.

ResponseTap’s CEO, Ross Fobian, said the data is significant as advertisers typically allocate online marketing spend to different devices based on the proportion of sales that can be attributed to them, suggesting that, until now, advertisers have been under-spending on mobile marketing.

The graphic below shows how the mix of total sales across devices is impacted by adding in phone sales.

“This data emphasises how important it is to track and analyse your telephone calls to fully understand how customers are researching and purchasing your products – only then can you ensure you are optimising your marketing spend,” Fobian said.

“We know that customers often want to speak to a real person before a purchase, but it’s now clear that this is particularly the case when someone is checking you out on a smartphone.

“It also shows far more shoppers begin their purchase journey on a smartphone than previously thought. Investing a higher proportion of marketing spend to attract their attention at that point will make sense for many brands.”

Sales made after a smartphone user has opted to call a business are typically not tracked as it has previously been difficult to attribute a phone-based sale.

ResponseTap does this by displaying a unique phone number to every individual person who visits a website on their smartphone. This means that when a customer makes a call it can be matched back to their smartphone web session.