Since the UK Government won't produce a detailed economic assessment / impact assessment of the EU Withdrawal Agreement Bill I thought I could provide some pointers - summary being the deal finds the perfect point to maximise future uncertainty 1/
First the good news for Government though - we could start our assessment by saying the deal delivers Brexit as promised by the referendum, and that for a future FTA relationship with the EU, global trade deals could deliver 0.4% to GDP (Nov 2018 HMG analysis) 2/
However, the same Government analysis suggests a future FTA relationship with the EU will potentially lead to a 6.7% hit to GDP (making some assumptions on migration any many other things) 3/ 
We can then add on the analysis conducted by @JohnSpringford on the economic cost to date of Brexit uncertainty - which is coming on 3%. This may also be relevant for the next period of "transition" 4/
@JohnSpringford Now there has been a hope for the economy to have a "Brexit bounce" once the uncertainty of a possible no-deal was removed. But given a transition period of only 14 months, in which time an FTA is unlikely to be negotiated, uncertainty continues 5/
@JohnSpringford Greenfield investment to the UK has been declining for the last three years as illustrated here by the FT, and the continued uncertainty about the future means this trend is likely to continue 6/ ft.com/content/bdc9f9…
@JohnSpringford Potentially we face two transition dates, Dec 2020, and then Dec 2022. The average EU FTA takes perhaps 5 years to negotiate, and we saw Brexit take over 3 years. No-deal is a possibility throughout. So the drag on investment continues 7/
@JohnSpringford Looking at particular sectors we get the good news that financial services and data equivalence could be in place by 2020. However the political declaration is notably weak on movement of people, which underpins so much UK services sector success 8/
@JohnSpringford Similarly in manufacturing there is some suggestion of regulatory alignment, and zero tariffs in the future, but the uncertainty about exact arrangements is likely to continued to depress new investments 9/
@JohnSpringford Looking at trade deals we have information missing on the status of UK participation in these during the transition period - the Commission is supposed to write to inform partners the UK should still be included. We don't know if all will accept 10/
@JohnSpringford The transition period does give the UK further time to negotiate with countries with which we already have trade agreements which have not yet agreed to replicate (e.g. Mexico, Canada), as well as start new negotiations (US, Japan, NZ) 11/
@JohnSpringford However new trade partners are likely to be cautious while the UK is negotiating with the EU, and we therefore don't particularly expect swift conclusion of deals. In some areas the UK will have to make a choice between EU and US approaches, which will not be quick 12/
@JohnSpringford For the next 1 or 3 years the UK will be implementing EU regulations without any say in them. Any impact assessment should probably be including what is known of these, and their likely impact 13/
@JohnSpringford Also included would be the extra costs the UK is likely to incur through Brexit, to an extent this is the increased staff costs for officials taking on Commission work (e.g. market access cases), but also infrastructure e.g. at Northern Ireland ports 14/
@JohnSpringford Bringing us on to Northern Ireland, where my impact assessment would start by suggesting that while details of GB-NI checks are not yet in place, there are very real security risks given that all goods on this route are subject to checks and customs 15/
@JohnSpringford Given there will be no checks on trade between Ireland and Northern Ireland it is likely that business will increasingly look to trade in that direction rather than with the rest of the UK. There are also questions on how long it will take for arrangements to be put in place 16/
@JohnSpringford When thinking about Northern Ireland we also have uncertainty on trade agreement coverage - is NI content going to count towards either EU or UK trade deals. There are reasons for and against. All this uncertainty means no early investment rush for the province 17/
@JohnSpringford We may also want to consider in our impact assessment that support for Scottish independence may rise, and that this is therefore a further risk to the future of the UK. Impossible of course to quantify for the UK economy as a whole 18/
@JohnSpringford So summarising, our Impact Assessment would suggest that the uncertainty over the UK's trading relationship in the coming years under this deal is extreme, with an inevitable knock-on effect for trade and investment 19/
@JohnSpringford In terms of policy recommendations, then, it would be to do anything possible to reduce uncertainty, whether longer transition periods, clear cross-party mandates for future relationships, and realism on future timescales. Unfortunately none of which we expect 20/ end
@JohnSpringford PS Forgot to add that there will yet be interesting discussions in areas like fish - where it cannot be guaranteed that UK will get any better deal than currently.
