But the conclusion doesn't suggest that the stimulus is ineffective, it suggests that it is counter-productive. I'd be willing to accept the conclusion that both types are ineffective, the conclusion that bother are counter-productive is well... odd.
Not particularly. If we assume that people are perfectly aware of Ricardian equivalence then they will be aware that:
a) Government spending involves a deadweight loss (you know better what you want than the government does)
b) The deadweight loss due to taxation rises approximately as the square of the size of the taxes, so lower taxes now at the cost of higher taxes later involves (with these very simple assumption) additional deadweight loss
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