Office rents in Manhattan, which have fallen for most of 2001, will rise again. About 2,5m m² of the New York island's more than 10m m² of space is no longer habitable. A 4% vacancy on September 10 became a 15% shortfall the next day when the World Trade Center towers fell, damaging other buildings. Some demand will spread to New Jersey and Long Island as groups move back offices away from high-profile buildings as a safety precaution.

Steve Mallen, chief researcher at International property consultants Knight Frank, says US groups want space in London, Vancouver and in other world financial centres, it seems to spread staff and limit damage if any one building is attacked.

Companies are questioning being in high-rise buildings,' adds Mallen. 'But I think that will be a short-lived issue.'