&gt; Firstly, she states that &quot;working class&quot; generally means &quot;without college degree&quot; - that doesn&#x27;t mean physical work.<p>No, but it in general greatly increases the likelihood.<p>&gt; Secondly, knowledge workers also get diminishing returns from longer hours, potentially with even more dramatic effect.<p>To their bodies? Or to the work they do?<p>Because that&#x27;s the difference, your body only takes that much abuse and then needs to re-charge. Go work a jackhammer for a couple of hours and let&#x27;s talk about diminishing returns.<p>&gt; Thirdly, many common non-physical working conditions are also extremely tiring mentally and damaging physically in the long-run.<p>Sure. Let&#x27;s talk after you&#x27;ve been hauling garbage for a day, been bent over under an engine hood or any other physically taxing workday. There is nothing that quite compares to being able to sit in a chair and think all day long and push a few buttons to wreck your ligaments, muscles and joints.<p>&gt; Finally, you&#x27;re implying that child-care is not physically exhausting.<p>I think you made that up, I did not imply that at all. As a father of 3 I&#x27;m more than aware of how physically exhausting child care is.<p>&gt; My impression of your response is that it has more slurs than the article, to be honest - just re-inforcing the primacy of manual labour. I have the impression you know what it&#x27;s like to work long hours in a stressful non-physical environment, so I find that odd.<p>An my impression of your response is that you would like all of the above to be true, however and for the record: I&#x27;ve done both. I&#x27;ve had a number of <i>very</i> physically intensive jobs when I started my career and to this day I&#x27;m grateful <i>every bloody day</i> that my life took a turn for the better and that I don&#x27;t have to work until I can&#x27;t stand up straight anymore. Being not the most physically strong person I realize that if I had continued down that path I would have been a physical wreck by now.<p>Have some respect for the people that do the heavy lifting. And if you&#x27;re unconvinced: go take a manual labor job for a year or so and re-read your comment here.