Consumers are fickle things. While dismayed UK investors watch the deterioration of margins at retailing stalwarts such as Marks & Spencer, difficulties on a greater scale are approaching retailers in the US. Not for nothing then, are the shares of the US retail property companies lagging the sector, despite an unusually high level of mergers and acquisitions. The difficulties facing some retailers, both in the US and Europe, have been well-documented. In August, The Gap reported results for the second quarter and warned that full-year profits estimates may be too high.

Analysts who keep an eye on retail on both sides of the Atlantic note several reasons why these are tough times universally. First, sharply higher oil prices are forcing people to rethink the number of shopping trips they make by car. And the rise in oil prices trims disposable income.

Second, interest rates are higher now than they were a year ago, making credit card purchases more expensive.

But a close reading of press releases suggests that painting a picture of retailing - and of retail property - with such a broad brush is probably to miss the point. The fact is that retailing and retail real estate are good in parts.

In a recent analysis of retail real estate investment trusts (Reits), property share analysts Green Street Advisors note that the shares of mall Reits have fared even worse than those of their tenants. By September, the S&P retail index had fallen 18 per cent in the year to date, while the mall Reits had fallen 21 per cent.

Green Street argues that the slowing in retail sales needs to be put in perspective; excluding automobiles, retail sales have been growing at a rate of 9 per cent, well above the 5 per cent average of the last 10 years.

Large retailers such as Wal-Mart, Sears and Federated Department Stores are still reporting sales growth on a same-store basis, meaning that each store is relatively more productive now than it was one year ago.

And even when a retailer experiences a tough spot, the reaction is not necessarily to shut stores. The Gap, which recently reported poor second quarter results and a profits warning for the full year, plans to expand store openings for its Gap and Old Navy brands by roughly 8 per cent and 24 per cent respectively.

Why then should retail real estate be undermined by a few poor quarters of retail trading? In the UK, the relationship between the fortunes of retailers and their landlords is equally pronounced. That is even more ironic given that leases tend to be far longer to expiry date and that property owners are insulated from falling rents on existing leases.

Nevertheless, the data suggests that retail property generally is underperforming the sector.

IS this justified? In the US, one factor beginning to undermine retail Reit shares is a growing number of tenant bankruptcies. Green Street notes that in recent months, Frederick's of Hollywood - the chain which claims to have invented the thong panty and sold the first push-up bra - has filed for protection from creditors, with 200 stores in US regional malls. Other casualties include Great Train Store with 56 stores, footwear retailer Joan and David with 67 stores, and Vista Eyecare with 908 stores. Many stores will remain open while the tenants undergo financial reorganisation, but some, surely, will close.

So-called strip malls, anchored by supermarkets and other convenience outlets, are similarly affected. Recent retailer filings for protection from creditors include Pic n' Pay Stores with 453 stores, homewares retailer This End Up with 135 stores, Noah Bagels with 539 stores, Stage Stores with 648 and Heilig-Meyers with 871 stores.

But Reit analysts note there is a fresh problem emerging for retail property owners. Analysts at Paine Webber point to the "slew of bankruptcy filings by national cinema operators over the past couple of months". Most recently, Carmike has filed for protection from creditors, while six others carry credit ratings assigned to junk bond issuers.

According to Paine Webber, roughly 7 per cent of the typical mall operator's earnings come from theatres. Although the impact on Funds From Operations - the benchmark used to measure Reit share values in the US - will be only modestly affected, some companies are particularly exposed.

Larger mall Reits, however, are far less dependent on earnings from this source and are better shielded from losses. These bankruptcies are occurring within one of the strongest periods of consumer spending in decades.

What is happening, analysts argue, is that retailing has entered a "survival of the fittest" environment with even the wealthiest consumers displaying cost-consciousness and changing tastes more rapidly than they did 10 years ago. Those cinema operators whose formats have not kept pace with the latest designs are worst affected. Apparel retailers who cannot adapt their formats are similarly hurt.

What does this mean for investors in retail real estate? The trading environment will be much more uncertain. Tried and true formulas cannot work indefinitely.

Green Street says: "Theatres are merely the latest example of periodic format changes in the retail real estate business, and although we can't say what changes are likely in the next five years, we don't doubt that there will be others."