Everyday passing by is a sample day that you can use to estimate the risks. Even if you argue that terrorism is a relatively new risk in the past few decades and start your sampling from September 2001, we still have more than a decade of sample days to estimate the risk. That&#x27;s a <i>huge</i> sample.<p>There might not be enough sample to know how many people would be harmed during a terrorist attack. But there is definitely enough information to estimate the risk of an attack itself.