Most of economics is about either efficiency or equity.<p>If you say &quot;let&#x27;s just tax fat&#x2F;old&#x2F;disabled people because they cost more so they should pay for it&quot;, that&#x27;s an equity argument.<p>If you say &quot;let&#x27;s tax fat people because by doing so you create incentives for being less fat&quot;, that&#x27;s an efficiency argument.<p>So it all depends on whether the tax has an effect or not (which is what the article is about) :)