Nordea says it's 30%

Analysts from Nordea on scenarios after the Brexit referendum:

In Q4 2016, the new Prime Minister triggers Article 50 of the EU Treaty by notifying the EU that the UK intends to leave. That opens a two-year window for negotiating a withdrawal agreement. But it seems unlikely that the ultimate relationship between the UK and the EU will be agreed within the two-year timeframe. 

Background: Last week PM Cameron said he would step down in the autumn and leave it to the next prime Minister to decide when to notify the EU about the intention to leave. A likely leadership battle within the Conservative Party could delay the government's invoking Article 50. Moreover, the new PM and his cabinet will need time to come up with a coherent plan for the future relationship with the EU (no such plan exists at this point). This could postpone the notification until early 2017, a risk which would be aggravated in case of an early general election in the autumn.