How do prices and output under oligopoly compare with prices and output under a pure monopoly and monopolistic competition? Now, how does this help define OPEC? At the same time, consider this: Many OPEC members ignore the quotas imposed, arguing that they need the petrodollars. Finally (and as we saw from 2014 into 2016), shale oil extraction allowed the United States to nearly become a net oil exporter, thus undercutting OPEC's ability to keep prices at $60 - $80 per barrel on the world market. It was decided that OPEC would continue to produce at higher levels, even when the average price per barrel would fall to $28 per barrel. Why then would OPEC do this even though the price would drop on the global market? Please be specific.