I own a three story apartment house.  The thermostat is in the hall on the top floor.It is set at 70 degrees.The tenant on the top floor is too hot and the tenant on the ground floor is to cold. The system is steam heat supplied by oil.  Where do I place the thermostat to satisfy both tenants?

If the top floor tenant is too hot (heat rises), and tenant on the ground is too cold, then moving the thermostat won't do anything. If you move it upstairs, the upper floor will be OK, but the lower floor will be freezing. If you put it downstairs, the guy down there will be OK, but the guy upstairs will cook. The difference between the two apartments will remain pretty much the same unless you add something to force hair to the bottom floor and away from the top floor.