-"Managing" is less visible than other kinds of work. Subordinate work tends to be almost all visible labor—crunching numbers, moving things, etc. This all but guarantees that subordinates will appear to be working harder—they are working harder on a physical level and humans are visual. Mentally, emotionally, and strategically, managers tend to have the more challenging job, but that depends.
Many managers do take advantage of the "behind the curtains" nature of their work and don't work as hard as they could. Others work themselves into the ground even though it may not seem like it. Like many things, this is a case-by-case deal.
To make it more tangible, I suppose a manager could write down how his/her time is spent (maybe an hourly recap). Even if it was just for a day, I think it would be enlightening for the company.
By:
Stephen Guise, answered on Quora