NEW YORK: Organic search, cost-per-click ads and email are significantly more important to online retail brands than Facebook and Twitter when it comes to actually selling products, research has revealed.

Custora, the marketing data business, analysed data from 72m customers shopping on 86 different retailer sites, tracking where they were clicking from, what and how much they bought.

It found that organic search was by far the most effective source of customers, accounting for 15.8% in 2013.

Over the previous four years, the percentage of customers that online retailers acquired via CPC had more than doubled to 10%, while the proportion arriving via email had quadrupled to almost 7%.

By contrast, the comparable figures for Facebook and Twitter were bumping along the bottom, along with banner ads, on less than 1%.

"I wouldn't necessarily say Twitter is inherently a bad way to do (online marketing), but we haven't seen a lot of good Twitter strategies right now," Aaron Goodman, Custora's lead data scientist, told Wired.

He added that current Twitter marketing campaigns were reliant on a consumer happening on a deal when they dipped into their feed.

When Custora looked at the value of the customers coming through each channel, similar trends were apparent over the four-year period reviewed.

Those who came to retailers from search were 54% more valuable than average, those from CPC 37% more valuable and email 12% more valuable.

Banner ads and Facebook, however, registered a 1% score on this metric, while Twitter customers were 23% less valuable than average. The report suggested the frequency of discount offers within tweets could be a factor here.

But emails could perform even better, as digital communications company Yesmail Interactive claimed that many are not optimised for mobile.

It said that more than a third of emails are opened on a mobile device, but more than three-quarters of marketers have only a basic mobile strategy that does not adapt email campaigns.

Half of consumers said mobile emails were difficult to read because they had to scroll too much.

Data sourced from Wired, Custora, MediaPost; additional content by Warc staff