Thank you for the update. Very informative.
You factor broken gear, but what about decommissioned hardware ?
When difficulty will go up, old hardware (1-100Gh/s) will eventualy be sent to the trash.
It may amount to 1-5 Phs.
I doubt they'll hash forever, even if some people have access to free power.
Eric
I think by the time hardware is decommissioned it will be so small as to not be noticed. For example if you try to find when cup mining stopped or gpu mining stopped. If everyone turned off their 300kh usb keys difficult will go up by 25% vs 25.3% next change. When 10gh blades are turned off it will be and increase of 25% vs 26% at next difficulty ect.