U.S. total online holiday sales may increase 13.5% year over year, reaching $151 billion in November and December, Forrester Research Inc. estimates.

In the 2017 holiday season, Forrester estimates that U.S. consumers spent $133 billion online, which includes both desktop and mobile devices. Forrester’s 13.5% increase for the 2018 holiday season is based on several factors, including increased consumer confidence and a strong economy, says Susan Wu, director of ForecastView at Forrester.

“H1 2018 retail sales grew faster than they did in the same quarter last year,” Wu says. “This robust consumer spending is a result of national unemployment that is near an all-time low, healthy wage growth and steady savings rates.”

The research firm’s healthy 2018 holiday sales e-commerce projection is in contrast to its in-store projection, which is a 1.7% year-over-year increase to $567 billion. Shoppers are increasingly using the internet to help with gift finding, Wu says.

“Shoppers are using more online sources than ever: apps, wish lists, online gift registries, social media and blogs have all gradually grown over the past three years,” Wu says. “By contrast, traditional sources such as circulars, catalogs, direct mail, magazines, television, radio and inspiration within a retail store have all declined over the same period.”

Forrester also estimates U.S. online shoppers will spend on average $785 each, which is 11% more than the 2017 holiday season. In addition, online holiday sales will account for more than 33% of 2018’s total e-commerce sales, making it an important holiday season.

Research firm eMarketer Inc. estimates higher e-commerce growth this holiday season, with a 16.2% year-over-year increase to $123.4 billion for total online sales in November and December. In addition, eMarketer also projects that mobile sales, including both smartphones and tablets, will increase a hearty 32.6% to $54.17 billion for the 2018 holiday season, up from $40.87 billion in the 2017 holiday season. Numbers are rounded.

It also projects that total retail sales will increase 4.1% for the 2018 holiday season, reaching $986.8 billion.

The National Retail Federation projects total retail sales in November and December to increase 4.3-4.8% to reach between $717.45 billion and $720.89 billion. This factors in both in-store and online sales, and the NRF does not have an online-only estimate.

Last year, the NRF estimated that holiday 2017 sales increased 5.6% over 2016. Although there is concern about the escalating trade war, the NRF still projects a holiday sales increase because of the healthy economy.

“With this year’s forecast, we continue to see strong momentum from consumers as they do the heavy lifting in supporting our economy,” says NRF chief economist Jack Kleinhenz. “The combination of increased job creation, improved wages, tamed inflation and an increase in net worth all provide the capacity and the confidence to spend.”

Internet Retailer released its holiday estimate in September, which projects U.S. consumers will spend $119.99 billion online Nov. 1-Dec. 31, which would be a 15.5% increase over the 2017 holiday season.