MENTION price cartels and many people will think of big, overt ones like the one OPEC runs for oil and the now-extinct one for diamonds.

提到价格垄断，很多人会想到一些大型和公开明显的垄断企业，如欧佩克石油输出国家组织以及现今已经退出市场的钻石垄断公司。