Mary Dejevsky: Happy hour? You must be off your trolley

What innocence! When I first read about Tesco, Sainsbury's and the like experimenting with "happy hour", I envisaged a qualitative leap in what market researchers would call my shopping experience. I could stroll around one of these mega-markets at seven in the evening, holding a glass of wine in one hand, steering the gleaming new trolley with the other, and making civilised small talk with my equally unhassled fellow customers. The weekly shop would start to resemble a private view evening at the National Gallery, the only real distinction being that you could – nay, should – take stuff off the displays.

Needless to say, my enthusiasm was not just premature, but ill-informed. Happy hour in new supermarket-speak is just another term for what in other areas of commercial life – planes, trains and hotels, to name but three – is known as "yield management". The idea (their idea) is to persuade you to do things you do not particularly want to do – like shop at an inconvenient time of day or take a holiday in a place and at a time when it is likely to rain – to help the provider maximise its profit.

The supermarket version of happy hour is to reduce the price of selected goods on particular days at particular times to convince you to go shopping. So, having become wearily used to the notion that a train ticket for the same route can cost anything from, say, £5 to £100, depending how far in advance you book, what time of day you want to travel and how many of you travel together, we must now apparently accustom ourselves to the variably priced kilo of low-fat margarine or litre of milk.

If you can make it to Tesco, for instance, in the middle of a Monday morning (when supermarkets are often empty), you may be able to knock pounds off your bill. But if you have to shop in the supermarket "rush-hour", no such reductions will apply. You will not only be subject to the usual deprivations – poorly stocked shelves, crowds vying for trolley-space and queues at the check-outs – you will have to pay more for those privileges.

Nor need the "happy hour" concept stop there. So flexible are the new high-tech pricing systems, we are told, that shelf prices can be changed almost minute to minute. Taken to its logical conclusion, managers could now raise or lower prices according to how many people are in the shop at any one time. You could even find that cut-price loaf of bread or bunch of bananas doubling in price if more than one pair of hands reaches for it at any one time.

Advocates of the system will inevitably say, as they say with planes, trains etc, that some people will benefit. But it is the supermarket chains that stand to benefit the most (why else are they doing it?), and many shoppers will lose. Like parents, who have little choice but to take breaks during school holidays – when fares automatically soar – people in full-time jobs working regular hours will find themselves paying premium prices if they want to shop at their convenience.

In one respect, "yield management" is merely an extension of the technology-assisted fad for auction and barter: priceline.com and e-bay brought to a supermarket near you. In another, it is a recognition that the club-card system of loyalty discounts has run out of success. It is card-averse shoppers like me, who look at the comparative price on the label and reject anything with a differential of more than 5 per cent, who limit its efficacy. Unfortunately, we can't exercise that sort of discretion if the price of everything rises just as our offices close.

Let me offer an alternative. If you want us to pay a premium, how about ticket-only opening on certain weekday evenings, with a glass of wine, perhaps, trolleys that steer and a little of that private view atmosphere? Now we are talking "happy hour".

m.dejevsky@independent.co.uk