The stringent version of &quot;the graphs look similar&quot; is called &quot;strong correlation&quot;, and there is some of that for the lead theory.<p>If you haven&#x27;t read it, the Mother Jones article is the place to start: <a href="http:&#x2F;&#x2F;www.motherjones.com&#x2F;environment&#x2F;2016&#x2F;02&#x2F;lead-exposure-gasoline-crime-increase-children-health" rel="nofollow">http:&#x2F;&#x2F;www.motherjones.com&#x2F;environment&#x2F;2016&#x2F;02&#x2F;lead-exposure...</a><p>That article has some critics that you can look up if you&#x27;re ambitious.