&gt; Do you really think everything the TSA does is literally 0% effective?<p>Yes, for the purpose of &quot;protecting American at large&quot;, it&#x27;s approximately that.<p>And it&#x27;s very simple to see too! The most effective way to prevent airplane terror is to stop everyone from traveling, are we gonna be safer thank to that, even disregard all the downsides of not being to travel? You know the bad guy can just plot their scheme elsewhere, right? What&#x27;s next? Millimeters scanner at Taylor Swift concert?<p>Also, since this is HN, I believe your maths is incorrect. The  effective rate is (100 - (100-x)(100-y)(100-z)...)%