Never mind the number of knots to the inch. Never mind the worn bits. American interior designers are going for a "look". For them, carpets with central medallions are out. Interlocking overall patterns are in. All because there are more ways of arranging furniture - especially the dining table - without a target-like blob in the middle of the floor. Pastel rather than strong colours are preferred - Americans expect their carpets to blend, not to show off.
Collectors of antique carpets, as opposed to home-makers who can afford only modern carpets, still buy for authenticity above all. But the fashion for overall patterns of foliage or birds, rather than medallions, has now spread from the modern to the antique market.
Western importers have imposed Western tastes on Oriental weavers ever since the British-Swiss Ziegler company, originally importers of cloth, opium and dried fruit, set up a carpet-buying office in Sultanabad in Persia in 1882. They specified no medallions and it is "Zieglers", "Ziegler Mahals" and "Sultanabads" that are back in fashion today.
Prices for bold-patterned, loosely knotted Turkish Ushak carpets, made in large quantities for stores such as Liberty and Maples from around 1890, and considered by some to be the "poor man's Ziegler", have benefited from the trend. Bonhams is offering one next week, estimated pounds 2,500-pounds 3,000. Most recently, auction prices for the more detailed, overall-patterned Tabriz carpets from Azerbaijan (north-west Persia) have surged, regardless of quality.
A cropped and worn 22ft by 18ft Ziegler of about 1880, estimated pounds 15,000- pounds 25,000 in Christie's October sale, sold for an astonishing pounds 57,600 to a trade buyer and is probably now gracing a New York apartment. For really mad prices for the right "look", New York takes the biscuit. In December, Christie's New York saleroom took $110,000 for a Tabriz with large-scale overall design, estimated at only $20,000-$30,000.
Home-makers with an eye for investment and only a couple of thousand pounds to spend should bear fashion trends in mind if they want their newly bought Oriental carpet to hold its value. Prices in the retail market are about 30 per cent down in real terms compared with 10 years ago, and British importers are ordering fine quality carpets - with the right designs - from India (not previously noted for quality), from skilled, refugee Afghan weavers settled in northern Iran, and even from Egypt. The market could be becoming overstocked.
Whether or not prices hold up, buying from a dealer who has driven down makers' prices is cheaper than buying from tourist bazaars in the country of origin.
Liberty's carpet buyer, Ron Stewart, reports big demand for strongly coloured high-pile gabbeh (unclipped) carpets made by the Fars people of Persia (now south Iran). They have simple, naive and sometimes abstract all-over designs, no medallions and sometimes no borders. The Western- influenced designs were introduced only six or seven years ago. An 8ft 6in by 5ft 3in gabbeh costs pounds 950 from Liberty in Regent Street, London.
Think twice before buying from cut-price bucket shops. Those 50 per cent reductions may be genuine - but all they mean is that the carpets have been displayed at some ludicrously inflated price for 28 days, in order to comply with trading regulations.
Yuda Ambalo, the 30-year-old Afghan who founded the Oriental Carpet Centre in Finsbury Park, which houses 30 dealers, has noticed that buyers for the home either rely on the advice of interior designers or get deeply involved, buying guide books, learning to understand designs and how to tell the difference between chemical and natural dyes. Above all, they shop around.
"City" carpets, hand-woven in urban factories from patterns, may have a comforting uniformity of quality and design, but there are no two tribal rugs alike. Tribal weavers "knot out of their heads" instead of following patterns. Mistakes and irregularities give tribal rugs their charm. But the only way to find out if you are being overcharged for one is to compare dealers' prices. Mr Ambalo also strongly recommends Tribal Rugs: A Buyer's Guide by Lee Allane, published by Thames and Hudson at pounds 8.95.
Modern Chinese and Pakistani carpets bear cryptic but helpful quality tags. A heavy quality 12ft by 9ft Chinese carpet from Liberty, priced pounds 1,000-pounds 1,200, will have a tag announcing "90-line 5/8ths super washed". A Bokhara-design Pakistan of the same size, of medium grade, pounds 1,300-pounds 1,400, will have a tag with the knot-count "11/22".
Price fluctuations can be purely political. Colourful flatwoven kilims from Afghanistan and Iran glutted the Western market during the Russian invasion of Afghanistan and the Gulf War, as weavers fled. A 8ft by 4ft Shahsavan kilim that might have fetched a peak pounds 750 up to 1990 could be had for only pounds 450-pounds 500 in 1995. Now prices are creeping back to 1990 levels.
The fear and uncertainty of new buyers has meant that carpet brokers and retailers who have earned recommendations for trustworthiness have prospered. Mr Ambalo recommends the Oriental Rug Gallery of St Albans, Eton and Guildford. Or commission a broker to bargain with wholesalers at a bonded warehouse.
Trends of the future? Towards more curvilinear Persian designs, perhaps, says Christie's William Robinson. He thinks that Kirmans, made near Fars, are undervalued. One in his forthcoming sale, with ice-blue field, fussy foliage - and a medallion - woven around 1880, is estimated pounds 10,000-pounds 14,000. And for long-term investors willing to buck the fashion trend, there is a traditional central Persian Kashan "Mochtasham" (the name of the original weaver) of about 1890, with strong colours, intricate design and medallion estimated pounds 12,000-pounds 16,000. You can buy a Kashan rug retail for pounds 1,200- pounds 1,500 today that would have sold for pounds 2,500-pounds 3,000 10 years ago.
Julian Blair, co-founder of the Oriental Rug Gallery, reports that, just recently, the Americans have started buying strong colours again. "Britain is usually about three years behind," he says.
The Battilossi carpet sale: Wednesday 2.30pm, Christie's, 8 King Street, London SW1 (0171-839 9060). Bonhams Oriental and European rugs and carpets sale: Tuesday 2pm. Oriental Rug Gallery: St Albans (01727 841046), Eton (01753 623000), Guildford (01483 457600). Broker: David Wilkins (0171- 722 7608).