In 1773 famed French astronomer Jérôme Lalande predicted that a comet would smash into the earth in 1789, destroying all life. Terror swept the country and church attendance skyrocketed.
But it was all for not. Lalande published his results and true enough, he predicted a disaster, but with only a chance of 1 in 64,000. As the panic subsided philosopher and mathematician Marquis de Condorcet noted that at least the sharp rise in unleavened bread boosted the economy.
The parable of the broken window was still 77 years away, so we can at least be sympathetic to the philosopher's poor economics. But that does not make the claim valid. The panicked purchase of leavened bread no more betters the economy than the purchase of bomb shelters during the Millennium bug scare. If it was truly this easy to grow the economy, then government agencies should relay false reports every few years predicting mass calamities. We'd be swimming in toilet paper, but we wouldn't be wealthier.
Source: The Measure of All Things. Ken Alder