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If we use the Sheldon Brown Gear Calculator set to metres development (although any other unit will work adequately), we see that the range for a 39-53 x 34-11 system is 2.5 to 10.4 metres developed per crank revolution, yielding an overall range of 416%.
Compare to a Sturmey-Archer AW three-speed hub, with an overall ratio of 178% based on its stated ratios of 1.33, 1.00 and 0.75.