These concerns about Keynesian spending are especially worrying because empirical support for the Keynesian model is far from compelling. The model implies that the impact of increased spending should be greater than the impact of tax cuts, but the existing evidence suggests more like the opposite. Indeed, some empirical evidence finds minimal impacts of spending, while most research finds a robust impact of tax cuts.

May I also suggest two items by Steven Kates: this short overview of Keynesianism and a video arguing against the claims made for aggregate demand.