In the fourth quarter of 2014, 47% of online retail traffic and 33% of online retail orders stemmed from smartphones and tablets, according to the Demandware Shopping Index, from e-commerce and m-commerce technology vendor Demandware Inc., which analyzed the activity of 100 million online shoppers at its 1,100 retailer clients worldwide during Q4 2014 and Q4 2013.

33.0% of traffic came from smartphones, up from 23.0% in Q4 2013; 14.0% of traffic came from tablets, up from 13.4%, Demandware says. 16.0% of orders came from smartphones, up from 10.0% in Q4 2013; 17.0% of orders came from tablets, up from 15.5%, Demandware finds.

Overall, on all computers and mobile devices, the average amount of time a customer spent per visit to an online retailer in Q4 2014 was 10.2 minutes, the index says. Average time spent per visit on smartphones did not drop much from the overall average: 9.6 minutes, Demandware says.

The vendor says in 2015, online retailers can expect smartphones to be the primary traffic driver and smartphones and tablets to by year’s end account for 40% of all orders.

Follow Bill Siwicki, editor of the Internet Retailer 2015 Mobile 500 and editor, mobile, of Internet Retailer, on Twitter at @IRmcommerce and @MobileStrat360B.