They are like an addictive drug to shoppers.
The retailers' marketing departments milk inherent failings in our caveman brains that drive even the most rational people to shop irrationally.
They go as far as playing tricks on us that turn on the tap of the feel good hormones in our brains.
The irony is that we pay more on Boxing Day than we would if we waited until January 29.
Way more in some cases. Vend's data shows that January 29 is the biggest discount day of the year, not Boxing Day.
Discounting levels in electronics and home furnishing stores increase by 49% in the last week of January compared to the last week of December, which covers the Boxing Day sales, says Vaughan Rowsell, Founder at Vend.
In fact four of the five biggest discounting days of the year are in January, Rowsell adds.
But the dark arts that is marketing uses research from neuroeconomists to overcome our logic.
Academics have found, for example, that triggers as basic as big red 'sale' signs in store windows send a rush of the feel-good hormone Buyagra (AKA dopamine) coursing around our brains.
And retailers know other little below the belt psychological tricks will open our wallets.
They use words such as "limited numbers", "today only", "new items" and "until sold" in their advertising to prey on our weakness for the concept of scarcity.
We're fooled into thinking we must buy now or miss out. With that they herd us to the malls on Boxing Day.
Another trick from the neuroeconomists is the concept of "anchoring".
We're encouraged to anchor our buying decisions on a meaningless price point.
At some stores, regular prices are high. So when they hold a 50 per cent off sale the price becomes more like the RRP elsewhere.
But the high anchor price means we think we've nabbed a bargain.
Likewise, "perceived value" is another related failing where we assume that a $300 pair of shoes on sale at $150 is better value than the $80 pair.
That's not always the case.
Then there's the "prospect theory" that says we're statistically more likely to buy a $95 item if the original price was $100 and we're getting a $5 discount than we would if the starting price was $90 and had been increased for inflation by $5.
They also get us, a McKinsey report pointed out, with 'buy now pay later' deals.
By delaying the spend retailers make the product's cost less psychologically painful, dramatically increasing our willingness to buy.
The antidote to this barrage of psychological cons is to treat shopping as a contact sport. Here's how:
Wait
If you stay home on Boxing Day you can't get herded into unnecessary purchases.
In many cases the impulse to buy goes away.
The Vend data and other numbers from comparison sites such as PriceMe shows that if you've got time, you'll get a better bargain by waiting.
I think the best deal in the sales is the one you don't buy.
We all think we "need" to buy whatever it is we happen to fancy at that instant.
Buy second hand
There are so many positives about buying lightly used secondhand goods. We do it with antiques, so why not other household stuff?
You can buy almost anything known to man on Trade Me. There are other tricks such as buying pre-loved, but guaranteed to work games from EB Games.
Shop with your smartphone and a list
If you must hit the mall, always take your smartphone with you when shopping for big ticket items such as TVs, perfumes, whiteware and so on.
That way you can whip it out and check the price on comparison sites.
Write yourself a shopping list and only buy what's on it.
Remember it's probably sunny outside, so the sooner you get out the better.
Buy online
If you really can't wait until January to buy something, then shop around online for that item only.
That way you're not walking past too many red sale signs and yellow stickered products that could con you into parting with money unnecessarily.
When MasterCard surveyed Kiwis it found that 41 per cent said they preferred to shop online to get Boxing Day Deals.
Finally, beware that retailers make money from upselling accessories and extended warranties.
The warranties often give you no more cover than the Consumer Guarantees Act.
