The US national production will be four times higher in 50 years

Harry Truman : president
In his 1950 State of the Union address, Harry Truman predicted that 'our national production 50 years from now will be four times as much as it is today.' In 2009, Time Magazine notes that in hindsight, 'it turned out to be more than 33 times as large'. 

State of the Union 1950 [speech],9171,1921587,00.html