The experts have been put out by the fact that, last month, we bucked the belt-tightening trend and splashed out in the shops at a faster rate than at any time in the past two decades.

After all, as the analysts huffed, consumer confidence is supposed to be at an 18-year low, house prices are falling and budgets are being eaten away by 3.3% inflation and painfully pricey fuel. So how to explain the so-called “City bombshell” that retail sales volumes in the three months to May went up by a sizzling 5.4% on the same period a year earlier, and May’s weekly average was up by 7% in value terms? Most analysts responded as if the Office for National Statistics was winding them up.

The Financial Times described the figures as “astonishing” and “staggering” given retail analysts’ predictions of a month-on-month fall. KPMG said they were an “anomaly”, Global Insight said they were “absolutely astounding” and Goldman Sachs called the numbers “frankly ridiculous”.

Experts sighingly attributed the ginormous (technical term, that) retail spend of £21 billion in one month to various theories: that the economy was healthier than everyone was saying; that the figures were wrong; that the sun suddenly came out in May after a whole year and everyone went shopping for summer clothes and the new scrummy ranges of ready-made picnic goodies in the supermarkets; and, lastly, that everyone just went mad and spent money even though they shouldn’t have.

Well, I have a different theory. What we saw in the shops last month, as money tightened and prices went up and we all felt poorer, was a textbook example of “girlie-nomics”, short for girlie economics.

Girlie-nomics explains everything about the retail sales figures, because - like the May shopping spree - it is reassuringly irrational.

Girlie-nomics is the process by which you discount the parking ticket you got while having your hair done by telling yourself that you didn’t have the whole head of highlights, just the half, so you actually saved money; and by which you rationalise the expensive designer jacket you just splurged on by telling yourself that you haven’t bought cheapo disposable high-street clothes for months, and then divide the price of the said jacket by the number of times you will wear it.

It is the process by which you go to the higher-end supermarkets and justify your higher spend on the finest luxury delicacies, such as the aged Jamie Oliver rib-eye beef, or the £15 Barolo, because you are saving money by staying in for supper, rather than going out (and it is no accident that in these straitened times Waitrose is expanding in bourgeois neighbourhoods as if there’s no tomorrow, and a Daylesford Organic Farmshop, not noted for its low prices and economy ranges, is opening a new west London superstore by Christmas).

Girlie-nomics is the calculator ticking constantly in a woman’s head, which reckons that buying an expensive face cream is worth it because it will save on Botox, and the holiday is necessary because otherwise you’ll get gloomy and unproductive, and so on.

If you don’t believe me, all I can tell you is that Verdict, the retail consultancy, agrees that the sectors behind the rise - food and drink, clothing and footwear, health and beauty - are female-dominated, and thus the impact of behavioural economics seems beyond doubt. This is true both nationally and in London, where monthly sales are up 8.2% year on year.

“While women are more active shoppers, fewer men are regularly shopping compared with last year,” says Maureen Hinton, lead retail analyst of Verdict. According to an as-yet-unpublished Verdict survey of 6,000 consumers, How Britain Shops, women’s participation is rising in six out of the eight retail sectors, while the proportion of male shoppers who regularly shop is lower in every sector except for electricals.

“In personal care we always see an upswing when there are hard times - beauty products are an indulgence women can justify. And shoppers are more selective when their spending is constrained. Instead of bulk-buying clothes in Primark, for example, profit figures show women are heading for shops like Burberry, Aquascutum and Mulberry.”

So now we know it really is true: when the going gets tough, girls go shopping.

The retail figures prove this. The sort of stuff that we buy on a daily basis - clothes, food, toiletries - are holding up, sales-wise. While the big-ticket stuff - like white goods, furniture, cars and male sectors like electricals, DIY, homecare, and music and video - well, aren’t.

So the promised retail recession hasn’t happened quite as those clever analysts predicted. Instead, largely thanks to women’s spending habits and men’s inability to reach for their wallets, what we are saving on big-ticket items, we are splurging on posh frugality at home - which makes for boom time on half the high street. It’s girlie-nomics in action.

- My husband likes to tease me about the fact that, for days at a time, I don’t leave my immediate neighbourhood. On 7/7, he never called to find out whether I was okay, because the chance of me being anywhere near the bombs was, he joked, “vanishingly small”.

Now I understand why I am reluctant to move further afield. One day last week I took two buses, six Tubes and a South West train, as well as driving to Sainsbury’s. I was at Sainsbury’s when it all started.

I’d decided to do the auto-checkout. I’d brought my own carrier, which I placed on the sort of metal tray sensor next to the scanning device. “Please remove item from the bagging area!” a loud robot voice kept commanding.

So I removed my bag, and meekly heaped all my items onto the metal tray, with the intention of packing them into my carrier after I’d completed checkout. This worked until a mango rolled off a caramelised onion quiche onto the floor. “Please return item to the bagging area!” the voice kept repeating, as if it had detected me in the act of shoplifting.

It went on all day. On the Tube, metronomic announcements told me when the next Circle line train would come, that there was “good service” on other lines, to stand clear of the closing doors and to use the full length of the platform. On the train, a voice told us where we were about to stop, where we had stopped and where we would stop next. Every two minutes.

What with all the people now holding conversations with their mobiles Apprentice-style - ie, holding them like individual spittoons, as if about to gob into them - and the constant toddler-level announcements, the notion of thinking or reading in transit is a thing of the past. So maybe I’m just a grumpy old woman who doesn’t get out that much. I can think of only one response to the nanny state of transport. To get out even less.

rachel.johnson@sunday-times.co.uk

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