• The economic analysis shows that the UK will be economically worse-off outside of the EU under most plausible scenarios. The key question for the UK is how much worse-off it will be post-Brexit.
• The failure of the UK to achieve an open trading and investment with the EU post-Brexit would have negative implications for the UK and EU, and provide little, if any, gain for the US.
• The option of leaving the EU with no deal and simply applying World Trade Organization (WTO) rules would lead to the greatest economic losses for the UK. The analysis of this particular scenario shows that trading under WTO rules would reduce future GDP by around five per cent ten years after Brexit, or $140 billion, compared with EU membership.
• The WTO outcome would likely move the UK decisively away from EU standards and result in significantly increased non-tariff standards, harming the ability of UK businesses to sell services to EU countries. The services sector, including financial services, dominates the UK economy, contributing to around 80 per cent of its GDP.
• Under WTO rules, the EU would also lose out economically, but nowhere near the same proportion as the UK. The economic loss to the EU could be about 0.7 per cent of its overall GDP ten years after Brexit.
• The seven other trade scenarios would be considerably better for the UK than WTO rules, but most would still lead to economic losses compared its current status as an EU member.
• Of all the scenarios analysed, the one that would have the most benefit would be a trilateral UK-EU-US agreement, essentially a TTIP-like agreement. The UK would be 7.1 percentage points of GDP better than the WTO rules scenario, which is even slightly better than continued EU membership would be. This is because the UK would gain preferential access to both the US and the EU marketplaces and benefit from their stronger economic growth attributed to a TTIP. However, a TTIP-like arrangement is seen as very unlikely in the current political environment.
• None of the ‘soft Brexit’ scenarios would be as beneficial to the UK as the trilateral UK-EU-US agreement. All three scenarios are likely to lead to modest financial losses to the UK economy compared to the current arrangement of EU membership.
• After Brexit, political and security effects would be the more important to the US. The potential economic gains and losses for the U.S. in Brexit are small, , apart from the TTIP-like arrangement which would result in substantial economic gains for the US. The US will miss the influence and global perspective that the UK brings to the EU decision-making process, particularly around foreign policy, security and defence.
• The EU is likely to engage with the UK during Brexit negotiations, but may see benefit in adopting a ‘zero sum game’ approach. Europe’s top political priority is to discourage other member states from withdrawing.
• It will be important for the UK to seek ways to move away from a ‘zero-sum game’ and towards a ‘positive-sum game’ as negotiations proceed, to ensure the best possible deal for all parties. A UK strategy of trying to pick apart European unity is unlikely to work since it is in the best interests of all EU member states to work together.
• Overall, it is in the best interests of the UK, and to a lesser extent the EU, to work together to achieve some sort of open trading and investment relationship post-Brexit. The “no deal/WTO rules” option would be economically damaging to both parties.

The full report was produced by Rand Europe and can be downloaded here;- https://www.rand.org/randeurope/research/projects/brexit-economic-implications.html