Offset pool, banking and borrowing flexibility, soft price collar using permit reserve auction at $ 28 per ton going to 60 % above three - year - average market price (sciencemag.org)
«Hard» price collar between $ 12 and $ 25 per ton, floor increases at 3 % + CPI, ceiling at 5 % + CPI, plus permit reserve auction, offsets like W - M (sciencemag.org)