Most retailers are optimistic about their chances of generating large online sales gains on Cyber Monday, according to a survey of more than 14,000 U.S. e-commerce companies by international shipping carrier DHL.

In fact, 52% of retailers expect their e-commerce sales to grow more than 21% during Cyber Monday compared with the Monday after Thanksgiving a year ago. That includes 23% of respondents that expect an increase of more than 40%. Just 22% said they expect no increase in Cyber Monday sales.

To help bolster their online sales, 27% said they will expand their information technology teams to support increased website traffic around Cyber Monday, and the same percentage plan to bring on more customer service staffers. 12% are increasing their mobile capabilities in some way. 34% of respondents are also offering additional express shipping options compared with last year.

Most retailers’ Cyber Monday plans have been in place for a while, the survey finds. 30% begin planning for Cyber Monday seven to 13 months in advance. 20% start five to six months out, 22% start three to four months in advance and 28% of the respondents begin preparing one to two months in advance of the event.

Those advance preparations could pay off, especially if Cyber Monday grows in 2018 at the same pace as last year. Cyber Monday racked up $6.59 billion in online sales—an increase of almost 17% over 2016, according to Adobe Insights. That made 2017’s Cyber Monday the biggest online shopping day in U.S. history, Adobe says.

When asked what their biggest business challenge preparing for Cyber Monday is, the No. 1 response, at 29%, was avoiding website malfunctions. Other concerns included the need to offer competitive shipping options (cited by 26% of respondents), maintain adequate staffing levels (23%) and fulfilling orders on time (22%).

As Thanksgiving weekend and Cyber Monday draw near, data from Adobe Analytics suggests there is reason for optimism among retailers that sell on the web. Adobe says U.S. consumers spent $18.1 billion online in the first 12 days of November. That’s a 16.6% increase over this time period last year. Adobe’s data is based on an analysis of trillions of visits to U.S. retail websites, 55 million unique products and transactions from 80 of Internet Retailer’s Top 1000 online retailers.