Shortly after The Economist wnt to press,about 25,000 people were expected to tum up at the London An Fair.Your correspondent visited just before,as 128 white booths were being filled with modern paintings and sculptures.Dealers clutched mobile phones to their ears or gathered in small groups.They seemed nervous-as well ihey mighl be."I can eam a year's living in one fair,"said one harried dealer while slringing up a set of lights.Before 1999 London had just one regular contemporary art fair,remembers Will Ramsay,boss of the expanding Affordable Art Fair.This year around 20 will be held in Britain,mostly in the cap-ital.Roughly 90 will iake place worldwide.The success of larger events such as Fneze,which star ted in London,has stimulated the growth of smaller fairs specialising in craft work,ceramics and other things.Artl4,which started last year,specialises in less weU-known intemational galleries,showing art from Sub-Sahuan Africa,South Korea and Hong Kong.One explanation for the boom is the overall gromth of the modem-art market.Four-rifths of all art sold at auction worldwide last year was from the 20th or 21st century,according to Artprice,a database.In November an auction in New York of modern and contemporary art made$691m,easily breaking the previous record.As older art becomes harder to buy-much of it is locked up in museums-demand for recent works js rising.London's art market in particular has been boosted by an influx of rich immigrants from Russia,China and the Middle East."When I sttuled 23 years ago I had not a single non-Westem foreign buyer,"says Kenny Schachter,an art dealer."It's a different world now."And London's new rich buy art differenLly.They often spend little time in the capital and do not know it well.Traipsing around individual galleries is inconvenient,particularly as galleries have moved out of central London.The mall-like set-up of a fair is much more suiLable.Commercial galleries used to rely on regular visits from rich Briions seeking to fumish their stately homes.Many were family friends.The new art buyers have no such loyalty.People now visit galleries mainly to go to evenLs and to be seen,says Alan Cristea,a gallery owner on Cork street in Mayfair.Fairs,and the parties thaL spring up around them,are much better places to be spotted.Some galleries are feeling squeezed.Bernard Jacobson runs a gallery opposite Mr Cristea.The changing art market reminds him of his father,a chemist,who was eclipsed by a pharmaceutical chain,in the 1960s.Seven galleries in Cork Street relocated this month to make way for a redevel-opment;five more may follow later this year.Yet the rise of the fairs means galleries no longer require prime real estate,thinks Sarah Monk of the London Art Fair.With an inlernational clientele,many can work online or from home.Although some art fairs still require their exhibitors to have a gallery space,increasingly these are small places outside central London or beyond Lhe city altogether.One gallery owner says few rich customers ever visit his shop in south London.He makes all his contacts at the booths he sets up at fairs,which might be twice the size of his store."It's a little like fishing,"he explains."You move to where the pike is."

Bernard Jacobson feels that

• A.gallery owners can make deals on the Internet
• B.many art buyers are trom non-westerm countries now
• C.the change of art markel has exerted pressure on him
• D.dealers can make a great deal of money at the art fair
• E.many people visiting galleries are not potential customers
• F.rich Britons regularly pay a visit to the commercial galleries
• G.very few art exhibitions were held al the end of the 20th century