Today's GDP figures are psychologically and politically crucial

London's Canary Wharf financial district Photo: Tim Ireland/PA Wire

There are important caveats to the GDP numbers we will get at 9:30 this morning.

They are likely to show a move of a few decimal points here and there - whether negative or positive the move is likely to be marginal.

The first assessment of the size of the economy will probably be revised. And GDP, like any statistics, can always be overplayed.

However, the GDP figures are probably the most comprehensive set of statistics we get. A negative number today could mark the start of an unprecedented triple dip.

Some economists will argue the economy is broadly flat whether the number is positive or negative, but it is psychologically important for the economy and politically crucial for the Government to know whether the economy is growing or shrinking.

It matters very much.