Black Friday is the busiest shopping day of the year, with customers queuing for days and sometimes even resorting to violence in order to get their hands on the best deals.

But the post-Thanksgiving sales may not in fact be the best time to snap up low-priced merchandise, according to a new analysis.

Researchers found that around a third of products advertised as being on sale for the holiday have been available at lower prices earlier this year.

More people than ever before are expected to abandon the tradition of family time  and head to stores to get a head-start on Christmas shopping or treat themselves to cut-price gadgets.

This year, the consumer frenzy has even spread to Thanksgiving Day itself – redubbed “Gray Thursday” – with a number of major retailers opening as early as 8p.m. to attract those who are keen to leave the house after a day of turkey and television.

In the past, the Black Friday sales have resulted in riots as customers compete to snap up limited bargains – but for many shoppers, the threat of violence is apparently worth it for the prospect of uniquely good-value deals.

However, an analysis by the Wall Street Journal and Decide Inc. has revealed that many products popular on Black Friday are actually available cheaper at other times.

Black Friday is the busiest shopping day of the year, with customers queuing for days and sometimes even resorting to violence in order to get their hands on the best deals

They surveyed more than 500 “doorbuster” bargains which have been promoted by stores such as Sears and Best Buy, and concluded that nearly a third had been sold for a lower price earlier this year.

The fact that Black Friday is not always the cheapest time to go shopping is not surprising, according to McKinsey’s Rob Docters, who suggested that many customers assume that the best bargains are available then without bothering to check prices on specific items.

“People associate Black Friday with good prices, and that eliminates the need to check price,” he told the Journal.

Sears is advertising the KitchenAid Series Stand Mixer at the special price of $319.99 this holiday season.

But in March, the same device was on sale at Sears for $296, according to Decide.

A spokesman insisted: “Our advertised prices are competitive.”

At Home Depot, a GE Adora dishwasher is advertised for $598, said to be a saving of $151.

But a Columbus Day offer in October pushed the price down to $538.

The company claims that the majority of its Black Friday deals are the best bargains of the year.

Other deals work out as uniquely cheap only when you include the value of gift cards given away with some items.

Experts told MarketWatch that while some items, such as gadgets and white goods, are particularly good bargains on Black Friday, customers should hold off for other purchases.

Winter clothing and linens, for example, tend to be cheapest in January as stores clear out their stock in preparation for spring.

And those hunting for deals on luxury goods such as jewellery are likely to be disappointed – retailers like Tiffany’s are too worried about the blow to their high-end image to offer any sort of Black Friday bargains.