&gt; A dramatic drop in violent crime since the 1970s because the &quot;self-appointed masterminds&quot; restricted lead.<p>I&#x27;m somewhat skeptical about that; while lead <i>may</i> be a contributor, there&#x27;s fairly strong indication over a long period of time of age demographics being a key driver in crime rates, and the curve of the crime wave is fairly consistent with that, making an <i>additional</i> explanatory factor unnecessary.