Interestingly , there was a post on here yesterday about OBR productivity predictions in the past . Worth noting , if these are wrong , and productivity is worse than forecast , then growth will likely be much worse than forecast as well . The biggest worry is also the chief uncertainty productivity growth . The Office for Budget Responsibility forecasts that rising hourly productivity could contribute 9 . 4 percentage points to overall growth of real gross domestic product between the second quarter of 2016 and the first quarter of 2022 . This assumes stagnation will cease but also that lost potential output , relative to precrisis expectations , will never be recouped . The UK is , as a result , far poorer than was expected precrisis , as a Resolution Foundation analysis of the Autumn Statement explains GDP per head is now expected to rise by a mere 6 . 8 per cent between the onset of the financial crisis and 2021 . It has also It has ignored , however , the possibility that lower trade intensity would reduce productivity in the long term . If you look at prebrexit forecasts , the impact of productivity is a huge driver for long term losses , models including productivity are more than twice as bad as those that do not include it . For instance NIESR ' s WTO scenario claims a loss of GDP of 3 . 2 % by 2030 , but if including productivity in their model this becomes 7 . 8 %. Also interesting and it ' s true , someone posted a summation on Twitter of how much they have overestimated growth in the past , sorry no linkFirst , like any forecaster , the OBR has got things wrong in the past . But it has , if anything , tended to be too optimistic on future output rather than too pessimistic . Second , the OBR ' s assumptions now put it among the more optimistic forecasters . Now this is not to say the OBR is wrong , but there is certainly scope for things to be worse , and their estimates are more on the optimistic side . Brexiteers should be happy with their estimates in that respect .