Cyber Monday was the busiest-ever online shopping day in the U.S., but data shows that on average, the websites of the 100 largest online retailers in the Internet Retailer 2016 Top 500 Guide fell short of expectations of how they should have performed.

Website monitoring and optimization firm Apica measured each of the Top 100 retailers’ sites based on such factors as site consistency, the minimum and maximum amount of time it took each site to load and how long it took each site to fully render before giving it an overall web performance score of 1-100. And Apica found that 50 of the Top 100 online retailers had pages that loaded in 20 seconds or more on the Monday after Thanksgiving, more than six times slower than what is considered a fast load time of three seconds or less. A 2010 report found that more than half of consumers—57%—“would abandon a web page after waiting three seconds for it to load.” This oft-cited three second baseline stems from a 2010 online survey from content delivery network and web security firm Akamai, which asked 2,763 U.S.-based respondents about their shopping behavior.

“Web performance is essential to completing transactions for e-commerce sites,” Apica writes in the report. “Multiple studies have demonstrated that load time has a direct correlation to sales. While research is underway to determine current shopper expectations, research has shown that about half of consumers expect a website to load in two seconds or less and that every extra 100 milliseconds results in approximately 1% drop in sales. 40% of shoppers abandon sites that take longer than three seconds to load.”

Though load times were much longer than normal, they didn’t stop sales from hitting a record high on Cyber Monday. Data from the Adobe Digital Insights unit of Adobe Inc. showed that U.S. shoppers spent $3.45 billion online that day, up 12.1% from $3.07 billion on Cyber Monday 2015.

Based on Apica’s methodology, Apple Inc. (No. 2 in the Top 500) had the highest web performance score at 94.8. Here’s a look at others in the top 10, as scored by Apica:

• Apple, 94.8
• The Home Depot Inc. (No. 7), 94.5
• Dell Inc. (No. 3), 92.0
• Rue La La (No. 80), 91.9
• Groupon Inc. (Groupon Goods is No. 26), 91.6
• American Eagle Outfitters Inc. (No. 63), 89.7
• Hudson’s Bay Co. (No. 75), 88.5
• Zappos (parent company Amazon.com Inc. is No. 1), 86.0
• Target Corp. (No. 22), 86.0
• Costco Wholesale Corp. (No. 8), 85.5

Those scores are well above the average score of the Top 100 retailers, which came in at 58 out of a possible 100. “We had hoped that this number was closer to 75/100 with Cyber Monday 2016 sales being the highest in history,” Apica writes. “As marketers, online retailers and e-commerce professionals look to measure the overall success of the campaigns and marketing strategies during this holiday shopping season—it is critical to also understand overall industry website performance, scalability and load capacity to understand what the shopper is experiencing.”

An Apica spokesman attributed the success of the 10 fastest sites to a number of factors, including those sites not relying as much on third parties to deliver content.