The economic news grows daily more grim. Across the developed world, once-optimistic forecasts for growth are being revised downwards. Financial markets, sensing trouble ahead, are in a tailspin. Debates over the future centre on a single metric – that of GDP.Gross domestic product was not always with us. Created in the 1930s, and despite the warnings of its pioneer, it rapidly assumed centre stage in economic policymaking. Growth could now be measured targeted through policy. For the right, it would be a simple gauge of national economic virility. For the left, it offered the more subtle appeal of an end to disputes over the distribution of wealth. By focusing not on the size of the slices, but on the size of the pie, an interminable conflict between capital and labour could seemingly be resolved. The case was put most forcefully in the Labour politician Anthony Crosland's influential book The Future of Socialism. Growth would deliver the public goods – secure employment and a functioning welfare state.