AN INCOMPLETE SET OF PRICES. British natural gas producers are paying gas companies to take immediate delivery.

Britain's gas storage capacity is 96% full so firms need to offload supplies. As domestic gas bills are based on longer-term contracts, consumers will have to wait for big reductions.

After trading at an average of 26p a therm through September, the spot price for gas delivered immediately fell to -5p during the course of the day, meaning traders are paying to get rid of it.

Ian Cook and William Polley make wry remarks about prices becoming negative. It's more accurate to note that tankage has an opportunity cost. It's cheaper for the well operator to hire the gas utility's tankage via what looks like a "negative" price for the gas than to expand its own storage capability.

Phil Miller considers a more complex case.

This happens in labor markets too where employers effectively pay some employees to retire.

Here, the unpriced good is the expected higher productivity of the replacement employee (because only relative prices matter, a less-productive entry-level replacement also satisfies the condition.)

I think it was Harold Demsetz who once quipped that a model of an economy that treated information as a scarce resource would look very different, very much as a model of a railroad that treated steel as a free resource would look very different from railroad that treats steel as a scarce resource. It's not so much prices that are negative occurring in practice as it is prices that bundle more than one good that provide the anomaly here.