A study conducted by the United Nations Conference on Trade and Development (UNCTAD) found that online sales accounted for nearly a fifth of the retail turnover in 2020.

The COVID-19 pandemic and subsequent lockdowns that were imposed last year were responsible for the rise. Online sales accounted for 19% of overall retail sales in 2020, a respectable increase from 16% the previous year, based on a survey conducted in major economies.

"Although it will take some time to get the full picture of the impact of Covid-19 on e-commerce, a number of developments point to the strong rise in e-commerce in 2020," said the study.

The study included data from Australia, Britain, Canada, China, Singapore, South Korea and the US. These countries are responsible for around two-thirds of online trade worldwide.

Online sales rose 59% in Australia, 46.7% in Britain, 32.4% in the US, and 14.6% in China.

The turnover increased by 22.4% last year to $2.5 trillion, having increased by some 15% in 2018-19. Retail sales overall declined by 1% year on year.

Data by gross merchandise volume (GMV) put China's Alibaba at the top, followed by US giant Amazon.

U.S. online grocery sales grew 54.0% in 2020 to reach $95.82 billion, according to the website Emarketer. That propelled it to a 12.0% share of total U.S. e-commerce sales and 7.4% of all grocery sales.

Looking ahead, it said growth would slow as the vaccine rollout allows shoppers to more comfortably return to stores.

Nevertheless, a portion of online grocery shopping will remain, pushing past $100 billion in spending for the first time in 2021, a full year ahead of previous estimates. And by 2023, online grocery sales will make up 11.2% of total U.S. grocery sales.