Interest rates are near zero – or moving towards it – in major economies worldwide. This column introduces a new theoretical framework that helps to organise thinking on how liquidity traps and slow growth spread across the world. It stresses the role of capital flows, exchange rates, and the shortage of safe assets. Once rates are at the ZLB, the imbalance between the supply and demand of safe assets is redressed by lower global output. Liquidity traps emerge naturally and countries drag each other into them.