Economic forecasting involves navigating the road ahead by the view in the rear-view mirror – it is no wonder that forecasts are so often wildly out.

But for all that uncertainty, the most important question arising from Tuesday’s revisions to the national accounts is what does the worst quarterly contraction since 1958 tell us about tentative signs of recovery in the economy?

One tempting answer is nothing. On the day that the economy moved into the third quarter, the news that the first quarter was worse than everyone thought changes very little. But that would be to underestimate the value of learning from the past.

First, the dramatic reduction in stock levels held by companies, some £5.4bn ($8.9bn) in the first quarter of 2009, will produce an inevitable bounce in growth in the months to come. As companies restart mothballed production lines national output will rise automatically.

The effect is potentially large. If stock building returned, for example, to the £3.1bn of the third quarter of 2007, the boost to growth would be £8.5bn. Alone, that would be enough to generate growth in the second quarter, even if the rest of the economy still performed as abysmally as it did in the first.

Second, a slump in “fixed capital formation” – investment in machines and buildings – has accounted for half the decline in national output in the year to the first quarter even though it accounts for only £1 in every £6 spent.

Half of the fall came from household investment in property, and a lot of that money is spent, to the irritation of almost everyone, on estate agent fees. Now that housing turnover has stabilised, this component is also likely to rise again.

Where the picture is more mixed is in household consumption. The bad news was that household disposable income fell 2.4 per cent in the first quarter. But this signal of household pain was mitigated by an absence of any sign that households have taken fright and are saving every spare penny they have. Household spending fell less than disposable income, resulting in a falling savings ratio, even in the depths of the recession.

Put the evidence together and the combination of this “rear-view” assessment of the future supports the notion of green shoots, at least in the months ahead. Growth is likely to return soon and might already have come back.

But the sting in the tail of this encouraging story is that a big part of the growth story results from the end of destocking – and the boost from this is temporary. Once the process has come to an end, there remains deep uncertainty over the underlying strength of the rest of the economy.