The largest financial crisis in history is spreading from private to sovereign entities. At best, Europe's recovery will suffer and the collapsing euro will subtract from growth in its key trading partners. At worst, a disintegration of the single currency or a wave of disorderly defaults could unhinge the financial system and precipitate a double-dip recession.

How did it come to this? Starting in the 1970s, financial liberalisation and innovation eased credit constraints on the public and private sectors. Households in advanced economies – where real income growth was anaemic – could use debt to spend beyond their means. The process was fed by ever laxer regulation, increasingly frequent and expensive government and International Monetary Fund bail-outs in response to increasingly frequent and expensive crises, and easy monetary policy from the 1990s. Political support for this democratisation of credit and home-ownership compounded the trend after 2000.

Paradigm shifts were invoked to justify debt-fuelled global growth: the transition from cold war to Washington Consensus; the re-integration of emerging markets into the global economy; the “Goldilocks” combination of high growth and low inflation; a much-ballyhooed convergence ahead of monetary union across Europe; and rapid financial innovation.