OBR UK growth forecast downgraded
The central forecast for 2011 is now for 2.6% growth, not 3.25% as in the Budget - though remember that Mr Darling's borrowing numbers were tied to a more "conservative" forecast of 3%.
Also, the OBR's estimate of structural borrowing - the part of the deficit that won't go away with the recovery - has been revised up, by 0.6% of GDP in 2010-11, or around 8bn.
That is despite the fact that the overall borrowing figures have actually gone down slightly for the period. That may partly be due to the fact that the OBR is basing its estimates on a central forecast for growth, not a conservative one. Spending is expected to be slightly lower than forecast previously - and tax revenues slightly higher.
The rise in the structural deficit is due to the OBR's decision to lower its estimate of trend growth - the rate that the economy can grow long term, without causing inflation.
In the Budget, trend growth was assumed to be 2.5% from 2010 (for the purposes of the Budget). The OBR thinks it will be 2.35% until 2013, then fall back to 2.1%.
For similar reasons, the OBR has cut the estimate of the amount of spare capacity in the economy at the end of 2009 - from 4% of GDP to 2% of GDP.
This is an important change. But the increase in structural borrowing diminishes a little over time. By 2014-15, the structural deficit is expected to be only 0.3% higher than forecast in Alistair Darling's last Budget. That is the kind of time frame Mr Osborne is looking at in setting his policy next week.
Update, 10:58: Sir Alan Budd and his co-authors are discussing their report with reporters now.
Sir Alan was keen to emphasize the point I made above - that these forecasts are not deliberately conservative in the way that past Budget forecasts were.
That means that, for example, they have ditched the extremely cautious assumption about future unemployment which was - by the Treasury's own admission - painting an inflated estimate of social security spending in the future.
Other things equal, getting rid of those assumptions would have lowered overall borrowing by more than the 3-4bn or so a year we see in these forecasts from 2011-12.
The key factor operating in the other direction - again, highlighted above - is the change in trend growth.
The best way to capture that change is that previously the Treasury thought that the crisis had caused a permanent loss of output of 5.25% of GDP by 2015 - around 70bn.
Now, the OBR puts that loss at 8.75% of GDP - that's around 120bn of "lost" income for the country as a whole.
However, the OBR would dispute that all of this was "lost" as a result of the crisis. In its view, some of it was never there - it was based on an unreasonably high expectation of how fast our economy could grow at a time of great demographic change, and slower immigration. In its view, that forecasting error pre-dates the crisis.
Given the scale of that change, it is perhaps surprising that the structural deficit by 2015 has risen by only 0.3% of GDP - less than 5bn.
Once again, Sir Alan would say that's understating the difference between this forecast and Mr Darling's - because this one has all those less cautious assumptions built into it.
However, as my colleague, Paul Mason, was able to get Sir Alan to confirm, that 2015 figure means that the OBR does think that Labour's policies would have eliminated a large part of the structural deficit by the end of the next Parliament. The OBR expects it to go from 8.8% of GDP in 2009-10 to 2.8% in 2014-15.
It is safe to say that Mr Osborne will want it to fall much faster.