资料题：The passage states that income available for spending in the U.S.was approximately how much greater in 1955 than in 1950（　）。

The economy of the United States after 1952 was the economy of a well-fed, almost fully employed people.Despite occasional alarms, the county escaped any post-war liquidation and lived in a state of boom.The history of extraction, production, and distribution had therefore been almost nothing but statistical table reflecting prosperity.An economic survey of the year 1955, a typical year of the 1950s, may be typical as illustrating the decade.The national output was valued at about 10 percent above that of 1954 (1955 output was estimated at 392 billion dollars).The production of manufacturers was about 40 percent more than it had averaged in the years immediately following World War I.The county's business spent about 30 billion dollars for new factories and machinery.National income available for spending was almost a third greater than it had been in 1950.Consumers spent about 256 billion dollars; that is, about 700 million dollars a day, or about 25 million dollars every hour, all around the clock.Sixty-five million people held jobs and only a little more than two million wanted jobs but could not find them.Only agriculture complained that it was not sharing in the boom.To some observers this was an ominous echo of the mid-1920s.As farmers' share of their products declined, marketing costs rose.But there were few pessimists among the observers of the national economy.Those few seemed to fear that the prosperity was based om government pump-priming(政府对商业企业的投资)on a stupendous( 巨大的)scale.