Total state spending as a share of national income is always one of the most informative statistics about the political economy of any society. It is the best single indicator of the balance between the public and private economies, and – in most modern western economies – the size of the welfare state. The one difficulty with it is that it provides just a little too much information, combining information on the overall size of the economy with the state in a single statistics. That can make it hard to interpret. In the early 1980s, for instance, the state's share in the economy surged – not, of course, because of Mrs Thatcher's largesse, but because manufacturing and the rest of the private sector was taking such a battering.

To some extent the contemporary spike in the series is another reflection of the private sector's constraction. But as my description of the path of this series under new Labour explains, there is more to it than that – in particular it comes at the end of a decade of proactive and expansionary social policies. Projecting the series forward, however – using data from the budget red book for the years up to 2013/14 and then imposing our own extrapolations based on the chancellor's assumptions about when the books will come back into balance – we can see that the series is set to take a nose dive in the years ahead.

DATA: spending as % of gross domestic product

GRAPHIC: how we visualised this data

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