The company's senior research director, Ranjit Atwal, said the decline could have been much worse, were it not for the increase in working from home.
"Government lockdowns due to COVID-19 forced businesses and schools to enable millions of people to work from home and increase spending on new notebooks, Chromebooks and tablets for those workers," said Atwal.
"Education and government establishments also increased spending on those devices to facilitate e-learning.”
Forty-eight percent of employees are expected to work remotely at least some of the time after the coronavirus pandemic ends, Gartner forecast, adding that this was up from a figure of 30% before the outbreak.
“This trend, combined with businesses required to create flexible business continuity plans, will make business notebooks displace desk-based PCs through 2021 and 2022,” said Atwal.
Another prediction was that while mobile shipments would fall by 14.6% in 2020, smartphones would fall by 13.7% to 1.3 billion units.
Atwal said: “While users have increased the use of their mobile phones to communicate with colleagues, work partners, friends and families during lockdowns, reduced disposable income will result in fewer consumers upgrading their phones. As a result, phone lifetimes will extend from 2.5 years in 2018 to 2.7 years in 2020.”
Affordable 5G smartphones had been expected to be the driver of phone replacements but the pandemic had knocked that on the head, with 5G phones only making up 11% of total mobile shipments for the year.
“The delayed delivery of some 5G flagship phones is an ongoing issue,” said Annette Zimmermann, research vice-president at Gartner. “Moreover, the lack of 5G geographical coverage along with the increasing cost of the 5G phone contract will impact the choice of a 5G phone.”
China was the only bright spot cited, with the country expected to continue its investment in 5G infrastructure, making it possible for Chinese providers to market 5G phones.