How much of the currently allocated IPv4 address space do you believe is unused? About half the ~ 40 legacy /8 assignments don't show up in the routing table.
Which, of course, means precisely nothing.
How much do you think a reclaim programme would cost to run? Don't know; don't care too much. Let the people who want the addresses pay for it.
I thought you didn't want a market?
Trading something that's in demand but has no supply will lead to hoarding, reducing availability or at the very least making it unpredictable.
The address space in question is already allocated, hence unavailable. The question is how to incent folks to put their "allocated but unused" address space back into play. Stamping your foot and declaring "markets are bad" isn't likely to be too helpful. Regards, -drc