This is correct, looking at the deficit as a proportion of GDP, and is a claim the government has made before.
Public sector net borrowing went from 9.9% of UK GDP to 3.8% between 2009/10 and 2015/16. That’s a decrease of just under two thirds. This year it is forecast to be 2.6%.
‘Public sector net borrowing’ is the headline measure of the government’s budget deficit. It’s the difference between the government’s income (mainly taxes) and everything it spends on public services, investment, and debt interest.
Borrowing as a proportion of GDP decreased because the amount the government borrowed over this time fell from £166 billion to £72 billion (in 2015/16 prices). At the same time the UK’s GDP also increased.
But the deficit didn’t fall as far as planned, as Mr Corbyn pointed out.
Mr Corbyn’s underlying point is correct: the government set deficit targets in 2010 (which it didn’t meet) and in 2015 (which it abandoned).
But when the government said it would balance the deficit by 2015 and create a budget surplus by 2020 it wasn’t referring to the same measure each time.
In 2010 the government promised to eliminate the “cyclically-adjusted current balance” by 2015/16.
This measure of the deficit ignoresinvestment spending. It’s also adjusted to take into account whether the economy is in a ‘boom’ or ‘bust’ period.
In 2015 the government updated its plans and aimed to have a surplus on public sector net borrowing by 2019/20. This is the wider headline measure we discussed above, which unlike the 2010 measure includes investment spending and isn’t cyclically-adjusted. This means that the government would have to reduce spending by more than under the previous target.
The government isn’t forecast to achieve this within the next five years, and new targets were set by the Chancellor last autumn.
Update 21 April 2017
We updated this piece with Mr Corbyn's comments and added a section on the government's commitments to balance the deficit.
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