In selling the stimulus to the American public last year, the Obama administration promised that the massive spending package would serve as a sort of Keynesian Red Bull, allowing the tired economy to keep partying hard. Instead, private sector output fell sharply and unemployment climbed. Yet Obama continues to defend the stimulus, aided in no small part by legally required reports issued by the Congressional Budget Office. But as Peter Suderman explains, those reports rely on assumption-packed models that effectively predetermine their outcomes. What they say, in essence, is that the stimulus worked because we assume it did.