Selling goods via online auction Websites such as eBay can boost the average UK household's wealth by about £3,000, says an economic consultancy.
Buying and selling online is becoming more and more popular, with more than 50,000 people in the UK taking part.
More than £4bn of trading is likely to be carried out on eBay alone this year, said the Centre for Economic and Business Research (CEBR).
This is the equivalent of 1.3% of total UK retail sales, the consultancy said.
Websites have increased the value of second hand goods by providing a cost-free platform for advertising them and maximising their sale price.
This has, in turn, boosted the value of goods lying around peoples' homes and consumer confidence in general.
"If people realise that they have sellable goods sitting in their cupboards, it ought to increase consumers' confidence just like any other unexpected boost to wealth," said Laura Phaff, one of the authors of the report.
In addition, the site could provide a hidden boost for retail sales, as sales from the auction house are generally not included in official figures.
And small niche traders are finding themselves able to tap huge national - and even global - markets, increasing the likelihood of making a successful and lucrative sale.
"Auction sites are increasing competition, widening consumers' choice and helping keep down inflation - both online and on the High Street," said Mark Pragnell, managing director of CEBR.