Every day, one hundred thousand tonnes of metal are stolen across the UK. This is mainly copper, although there is a significant amount of iron also.
All of this metal needs to be replaced, as most of it can be quite vital to railway lines, the structural integrity of houses and stopping cars falling down the holes in the road where manhole covers used to be.
When the metal is replaced, it increases demand for the metal.
"It's simple economics," said economist, Matt Doore. "More demand, more cost."
As the value of the metal increases, the more tempting it becomes for metal thieves.
"Metal thieves are basically driving the spiralling cost of metal," said Doore.
Metal thieves are stealing anything, from piping to buses. They are even stealing stolen metal.
"We even caught somebody trying to dismantle a bridge near Newcastle," said Jenn Darme, detective in charge of Newcastle's Metal Theft Division. "Fortunately, they'd already stolen the train, and the tracks, so there was nothing to fall off the bridge had they been successful."
Economists believe that this is the first instance of a feedback loop in theft.
"You see feedback loops in nature, physics and even economics," said Doore. "We've not seen it in crime before. Life, eh? Always full of surprises."