For the first three weeks of 2008, US businesses and consumers continued to ship packages and parcels ahead of the pace they set a year earlier, undaunted by a spate of gloomy headlines and government reports on the weakening health of the nation’s economy.

By late January, as though corporate America’s optimism that the downturn would soon pass had drained, they began to slow, according to United Parcel Service. UPS, the world’s biggest package-delivery company, announced on March 12 that volume at its domestic business was mired in a six-week slump.