• by Mark Walsh  @markfwal, May 8, 2014

By 2018, that figure is predicted to more than double to $65 billion, growing 31.6% on average annually. Keep in mind that the desktop will remain the place where most online bookings take place. Mobile will account for 18% of all digital travel sales -- including leisure and unmanaged business travel -- this year, and 37% in 2018.

In addition to the continued proliferation of devices, eMarketer says the shift toward mobile sales is driven by companies developing more mobile-friendly services. “The ability to purchase anything anywhere at any time via smartphones creates significant opportunities in the travel space in particular, given that its consumer base is by nature mobile,” states the report.

As a result, last-minute bookings by smartphone are helping to increase mobile sales, albeit for smaller transactions like overnight hotel stays and short-term car rentals. In that vein, TripAdvisor recently rolled out direct booking of hotels through its mobile site and apps. But so far it’s available to only about 10% of U.S. users.

Tablets present a different use case. Because of their lean-back nature, they are more likely to be used at home for travel planning. That means longer trips are typically booked via tablets, leading to larger transactions.

The eMarketer report doesn’t break out travel sales by smartphones versus tablets. But recent research by the firm indicates that about 75% of all “mobile bookers” are using both devices to make travel purchases throughout the forecast period.

A separate study this week by Millennial Media (with comScore), however, showed that travel still lags other industry categories in time spent shifting to mobile. The data indicated 68% of time spent on travel content takes place on the desktop, with 11% on tablets, and 22% on smartphones.

By comparison, 53% of time spent on retail sites now happens on smartphones and tablets.

As a mature e-commerce category, travel overall is seeing slowing growth relative to retail. Last year, it accounted for 34.1% of the nearly $400 billion U.S. e-commerce market. In four years, it will make up only 26.2% of the estimated $666 billion total.

Looking just at mobile sales, however, travel is gaining share within the m-commerce arena. It is expected to make up 31.1% of all U.S. B2C m-commerce sales totaling $84 billion this year, and increase to 32.8% of a projected nearly $200 billion in 2018.

"Businessman with mobile phone at the airport" photo from Shutterstock.