HIGH-VALUE banknotes have been getting a lot of bad press. In February 2016 the European Central Bank announced an investigation into the use of the €500 ($549) note; soon afterwards Peter Sands of Harvard University published a report arguing for its withdrawal, along with big bills like the SFr1,000 note ($1,000) and even the $100 bill. Why are big banknotes falling out of favour? For most people, large notes can be a liability, rather than an asset. Swanky shops in central Zurich will accept large notes in payment for posh fountain pens, though they use special machines to check they are not fakes. But try to pay for a taxi ride or a chocolate bar with a large note and you will be met by funny looks at best, and a flat-out refusal at worst. Most places will not accept them, and most Europeans have not even set eyes on a €500 note. Despite this, central bank statistics reveal that they are peculiarly popular: 60% of Swiss francs in circulation are in the form of SFr1,000 notes, and 30% of cash euros are in €500 notes. Some suspect that most high-denomination notes are in the hands not of anxious savers, but of criminals.

Working out exactly who holds cash is a tricky business; that, after all, is part of its attraction to lawbreakers. But law enforcers are sure that large notes are criminals' currency of choice, being compact and easy to hide. Recently, concerns have arisen over the role of large bills in financing terrorism: a courier for jihadists caught travelling to Turkey in 2014 with 40 €500 bills (€20,000) in her underwear would have needed very much larger knickers to transport the same sum using €100 notes. But David Lewis of the Financial Action Task Force, an international body that co-ordinates efforts to prevent criminals using the financial system, says high-value notes are used mainly in drug- and people-trafficking, money-laundering and racketeering. Mr Sands also argues that withdrawing them could help fill government coffers, by making tax-evading cash-in-hand payments harder.

Getting rid of large notes might also hinder criminals: bulky piles of cash are easier to spot. But the process is not straightforward. Any withdrawal would have to be slow: central banks worry that putting an expiry date on cash could undermine the value of their currency. This will disappoint those hoping that eliminating high-value notes will prompt awkward conversations between criminals and the authorities. There is political resistance too; some worry that abolishing large notes might be a step on the road to abolishing paper money altogether. And without a coordinated withdrawal of all such notes, the move would be much less effective. The Swiss authorities have no plans to get rid of their Sfr1,000 note. But big-bill haters argue that in the business of making life harder for criminals, every little helps.

Update: This blog post has been amended to remove the news peg.