Ann: Atlas Suspends Production in Response to Low Iron Ore Price, page-34

Barnett needs to work it so if you produce over say 200 million tonnes, double or triple the royalty - or tier it in the 200+, 300+ million tonne scale. The State Treasury then receives extra revenue to help balance the books and make up for the shortfall with the plunging price due to excess production - they need this to stop the massive deficit. They need to work it so it makes financial sense for the big miners to reduce production, so they pay less royalties and the higher ore price maintains their margin.

It's not in the States in the interest to have the ore ripped out of the ground at an accelerated pace to receive less money for the same.