Mueller and Stewart estimate that expenditures on domestic homeland security (i.e., not counting the wars in Iraq or Afghanistan) have increased by more than $1 trillion since 9/11, even though the annual risk of dying in a domestic terrorist attack is about 1 in 3.5 million. Using conservative assumptions and conventional risk-assessment methodology, they estimate that for these expenditures to be cost-effective “they would have had to deter, prevent, foil or protect against 333 very large attacks that would otherwise have been successful every year.”
