New Zealanders spent about $13.8 billion on retail food and beverages last year - a huge chunk of it from supermarkets. But supermarkets have a few tricks up their sleeves to encourage shoppers to part with even more money than they planned.
Dr Bodo Lang, from the Department of Marketing at the University of Auckland, says supermarkets are like their own miniature cities, tailor-made to entice shoppers into spending money.
"This is done by making you spend as much time in the supermarket as possible and making you deviate from your plan."
Having a budget and knowing what to look out for are the best ways to avoid over-spending.
Oh, and don't buy groceries when you're hungry ...
Even before you walk into a store, supermarkets have already worked their magic, Dr Lang warns.
"They are all designed to give a particular impression."
For example, Pak'n Save stores are "barren, exposed, have concrete floors [and] really high ceilings", he says.
"It gives the impression that effectively they don't have any back costs ... and all the savings are being passed on to the shopper."
But, this is not always the case. "It's about perception. Supermarkets work to influence the consumer's perception of what they're like through store layouts, floors [and] aisle widths."
Countdown supermarkets, for example, which are generally considered more upmarket than Pak'n Save stores, may be just as cheap pricewise, Dr Lang says.
"The key is perception."
Supermarkets have fresh fruit and vegetables at the front because they tend to put shoppers in a good mood.
"From the supermarket's perspective ... it sets you up for a really profitable shopping journey."
Consumers are more likely to indulge in other items once they have the healthy things like bananas and broccoli in their trolley, he says.
"Shoppers say, 'If I already have a few items in my shopping bag, it's ... easier to justify putting another bag of potato chips in'."
Consumer NZ warns that staple items like bread and milk tend to be at the far side of the building so shoppers have to journey past countless other products to pick up the basics.
Sweet treats and confectionary are often placed on low shelves to attract children.
END OF AISLE DISPLAYS
Just like in cities, supermarkets have "prime real estate" spots, which are the most sought-after locations to display products.
"Ideally where you want to be is in the best possible position ... which is at the end of each aisle," Dr Lang says.
"That's where people turn, they reorient themselves [and] their shopping habit is basically broken."
Manufacturers pay more for an end-of-aisle display spot because products tend to sell faster.
APPEALING TO THE SENSES
The bakery or deli section is usually positioned close to the entrance and smells divine, encouraging us to splurge on unintended food purchases, Dr Lang says.
"Basically, the part of our brain that perceives smell is very, very closely linked to very primitive parts of our brain.
"It's all very fresh, very beautifully presented ... and probably just gets you a little bit more hungry ... which is exactly what supermarkets want."
Vouchers and instore "homebrands" can save you money. But consumers need to be wary of special offers which often come with a catch, Dr Lang warns.
One of the best "tricks of the trade" is to have limited offers for products.
"What this does is create a sense of urgency and a sense of scarcity in the consumer.
"As soon as you say, 'special limited to two per person' - people are more likely to buy."
When considering specials, shoppers need to evaluate whether it's cheaper than rival products, and if they're changing their consumer habits or deviating from their purchase plan.
"If they are, then they are not really making any savings."
The New Zealand Federation of Family Budgeting Services has several tips to help keep your grocery shopping bill in check:
Make a menu for the week and write up a list from this.
Stick to your list and budget.
Be careful of specials because they may not be the cheapest option.
Shop around - check out local markets and different supermarkets.
Leave your children at home.