Election 2017: Methodology for manifesto guide

The Election 2017 guide to parties' policies has been put together by the BBC's Visual Journalism team, working with our News Analysis team in London and specialists in Belfast, Cardiff and Glasgow. It will be updated as parties publish their general election manifestos.

How were the issues chosen and ranked?

The 10 policy areas are based on those highlighted in Ipsos Mori's Issues Index, which measures the issues that the public believe to be the most important facing the country. Members of the public are polled, with questions designed to elicit spontaneous answers, which means respondents are not prompted to choose from a list of pre-selected issues. Where there is a crossover between some issues they have been grouped together for simplicity, eg "NHS/hospitals/healthcare" and Ageing population/social care" have been group under the headline issue of "Health and care". The most popular issues were then chosen based on their aggregate score over the 12 months prior to April 2017. Some issues, such as Future of the UK were added on editorial grounds to fulfil the BBC's public service commitments. Issues have been ranked in the guide based on their aggregate score of importance, from most to least important.

How have parties been chosen and ordered?

Any party represented by at least one MP during the course of the 2015-2017 Parliament, is represented in the guide, at UK level. The Alliance Party of Northern Ireland is also represented in the guide, as it has evidence of significant political support and is fielding candidates in all 18 constituencies in Northern Ireland. Parties are ordered by number of seats held (and then alphabetical order if tied). At "nation" level, parties are included and ordered by number of seats held at Westminster.

How are the policies selected and summarised?

This is an editorial process overseen by BBC journalists. For those parties due to launch their manifesto after the publication of this guide - this guide will be updated.

What about issues that are devolved from the UK parliament to national assemblies/parliaments?

Because of devolution, the UK parliament cannot rule on, or has limited powers over, some of the issues highlighted in the guide. For example, "health" is devolved to Northern Ireland, Scotland and Wales, so voters in these nations will not see the result of parties' Westminster health policies. Yet, some parties have been campaigning locally on these devolved issues in the run up to the election, and voters may still be influenced by these parties' views. In such cases, the guide makes a clear distinction between policies and "campaign points".