The table below is from the neutral Congressional Budget Office.
Now, as I’ve said before, multipliers are probabaly a bit lower in the UK than in the US (we have a more open economy and so spending is more likely to “leak” abroad), but this is still important.
The concept of the multiplier is simple – it measures the effects of changes in fiscal policy on the economy as a whole. A multiplier of 1.0 means that a one pound change in policy effects GDP by one pound. A mutliplier of 1.5 means a one pound increase in policy increases GDP by £1.50p. 0.5 means a £1 change in policy moves GDP by 50p.
Notice that tax cuts on low and middle earners will be more stimulating to the economy than tax cuts on high earners. Notice too that generally spending is a more effective means of getting growth than cutting taxes and remember that these multipliers work in reverse to – so cutting spending is likely to hit growth harder than raising taxes.