A three-year survey of bidding behavior on the online auction site eBay shows what to avoid if you want to get a bargain: lots that are illustrated, lots from regular sellers, weekend bidding and long auctions.

The research, conducted on the California-based site eBay, showed that if you buy an item that is illustrated with a photograph, it could set you back by an extra 11 per cent, compared to a similar item without a picture. And merchandise sold during the weekend costs about two per cent more.

The study was conducted by Charles Wood of the Mendoza School of Business at the University of Notre Dame in Indiana and his colleagues at the University of Minnesota. They looked at the sale of coins on eBay from 1999 to 2001.

In addition to the weekend and picture effects, they found that auctions that last longer attract more bidders and end up pushing prices up. Also, more experienced sellers are able to attract higher bids, based on their reputations. William Robinson, head of Islamic art, rugs and carpets at Christies auctioneers in London, says the study?s conclusions ring true. In live auctions, he says, reputation tends to help push the price up, whether it is the reputation of the auction house or the auctioneer. ?They do make a difference, because the buyers feel comfortable with them,? he says.

He speculates that people are willing to pay more during evening sales than during the day because evening auctions are more about recreation than business, and people are willing to bid more when buying for themselves.

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