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. But at least as damaging are the many secret cartels in such unglamorous areas as ball-bearings and cargo rates, which go on unnoticed for years, quietly bumping up the end cost to consumers of all manner of goods and services.

Collusion among producers to rig prices and carve up markets is thriving, with the cartels growing ever more intricate and global in scope (see article). Competition authorities have uncovered several whopping conspiracies in recent years, including one in which more than 20 airlines worldwide had fixed prices on perhaps $20 billion of freight shipments. They were fined a total of $3 billion; and so far the compensation claims from ripped-off customers comfortably exceed $1 billion. One academic study found that the typical cartel raised the price of the goods or services in question by 20%. Another suggested that cartels were robbing poor countries’ consumers of tens of billions of dollars a year: if so, negating all the aid that rich countries’ governments send them.

Investigators are still unravelling a huge global network of cartels among suppliers of a wide range of car parts. Makers of seat belts, radiators and foam seat-stuffing have had hefty fines slapped on them. Earlier this month the European Commission fined five makers of automotive bearings a total of €953m ($1.32 billion). This week its investigators raided a bunch of makers of car exhausts. Also in recent days, Brazilian prosecutors have charged executives from a dozen foreign train-makers accused of rigging bids for rail and subway contracts in the country’s main cities. Price-fixing has infected high finance, too. Some of banking’s biggest names stand accused of fiddling interest-rate and foreign-exchange benchmarks.

The good news is that enforcement has got tougher, smarter and more co-ordinated. Gone are the days when price-fixers got a slap on the wrist. Firms can expect swingeing fines, and bosses can go to jail. Since many cartels now operate across borders, so do investigators: American and Japanese trustbusters joined forces to flush out the car-parts cartels. And incentives for whistleblowers have also increased: around 50 countries now offer immunity or reduced penalties for snitches.

That is all for the better, but the penalties for price-fixing remain too mild. The best study of the issue so far concluded that, given the still-low risk of detection, collusion pays. Yet beyond a certain point—which the fines now imposed by American and European regulators have probably reached—fines inflict so much damage on guilty companies that they undermine competition instead of enhancing it. The answer is stiffer prison sentences, particularly for senior executives. American courts, only too ready to lock up other types of miscreants for a long time, have rarely jailed egregious price-fixers for anything like the maximum of ten years that the law allows. Other countries have even more scope to increase sentences.

Buy some geeks

More can be done to aid detection, too. Statistical tests to “screen” markets for unusual pricing patterns helped uncover the interest-rate and foreign-exchange scandals. Potential conspirators may think twice if they suspect their market is being screened. European and Latin American trustbusters are making good use of the technique; their American counterparts should do so, too. Deploying such cutting-edge technology is costly; and increased funding is a big ask at a time of public-sector parsimony. But cartel authorities in Europe and America generally bring in far more than they cost to run, so extra money pushed in their direction is likely to be well spent.

Another way to discourage the formation of cartels is to factor the increased risk of collusion into scrutiny of proposed mergers. Price-fixing is likelier, and easier to sustain, with fewer players. This could never be the primary determinant in competition decisions, but it should be in the mix. Blocking a few more mergers—whose benefits anyway tend to be over-egged—might both save companies from themselves and spare their customers the costs of collusion.