1. How did you get the data?
2. What is the FTSE 100?
3. Have you missed a company?
4. Are there any errors in the data?

5. Are there duplicate companies?
6. What does 'percentage owned' mean?
7. What are the income groups?
8. Where is your list of tax havens from?

This research is based on information that had never been disclosed, let alone analysed until this year. UK company law compels companies to report all of their subsidiary companies, together with their country of registration. Companies should include this in their annual report or, where the comprehensive list is of excessive length, they can include it within their annual returns filed with Companies House.

When we started to looked for this information a year ago, we discovered that more than half of the FTSE 100 were not complying with this legal obligation.  When enquiries to individual companies failed to persuade them to disclose the information, we submitted complaints to Companies House, forcing companies to re-file their annual returns with the information included, and sparking sparking Vince Cable to announce the launch of an investigation

Having compiled a full set of subsidiary listings, ActionAid was assisted by company information specialists Duedil to process the data into a useable format.  The annual returns, which in most cases were available only as scanned PDF files from Companies House, were converted to text using Optical Character Recognition (OCR) software, after which extensive corrections were made.

You can download all the data via Google docs

The FTSE 100 is a list of the largest 100 companies listed on the London Stock Exchange, measured by market capitalisation

The composition of the FTSE 100 changes regularly. We used the index as it was composed on 26 July 2011, to give us time to submit complaints against any new constituents that did not comply since our major complaint was submitted earlier in the year. Since that date, two groups have been replaced in the official index.

We used the annual returns that were available on the Companies House website on that date, although the lists for a few groups are more recent because they were obtained through a complaint submitted on that date. Some groups may have filed new annual returns with updated subsidiary lists since the 26 July, but we have not taken this into account because of the time required to turn scanned PDF files into usable data.

The lists of companies are disclosed by the parent group, but not verified by Companies House. ActionAid has taken this information on trust. Not all companies have used the same criteria to determine their lists (see question 6) which may mean that some may have omitted companies often connected to them.

Eight of the FTSE100 are listed in London but registered offshore, and are only obliged to disclose their 'principal' subsidiaries in their annual accounts. We have used these abridged lists, apart from for WPP, which had filed a much larger list with the Securities & Exchange Commission in the United States.

We were unable to obtain comprehensive lists of subsidiaries for two UK-registered companies (John Wood Group and Wolseley) in time to include them, and so have used the principal subsidiaries listed in their reports.

There are a few typing errors in the data, because we had to used scanned PDF files, sometimes with poor legibility, and convert them back into text. Sometimes the software we used makes mistakes when reading documents. For example, 'America' often comes out as 'Amenca'. We checked through the data afterwards, but with 35,000 entries it’s inevitable that some errors crept through. It looks to us like there were some errors in the source documents, too, but we’ve tried not to correct these unless we were sure about them.

If you think you have found a duplicate, please check and make sure that you have as sometimes companies with the same name exist in different countries.

Despite our efforts to make sure the data is accurate, there are still some duplicates, for three reasons:

>> Some groups submitted lists of companies in tree structures. Because multinational groups often have complex joint ownership structures, many companies within them crop up in these diagrams several times. We tried to remove these duplicates, but OCR errors combined with the odd inconsistency in the source documents means we may not have removed them all.

>> Some multinationals seem not to be entirely sure themselves! Apparent duplicates, with slightly different names, crop up in several of the source documents. We haven’t removed them unless we were sure they were duplicates.

>> Some companies are joint owned by two or three different FTSE-100 groups, and crop up in all their lists. So they will appear two or three times, within the lists for each parent group.

First, the definitions:

>> A subsidiary is a company in which the parent group as a controlling stake. Usually that means it owns more than 50% of the shares, but sometimes share structures are more complicated than this.   

>> A joint venture is one in which the partners all have an equal share, and none has overall control.

>> An associate is one in which the parent group has a major shareholding, but not a majority. Typically this is 20-50% of shares.

Some companies give only lists of subsidiaries, while others list all three types with the percentage ownership. Percentages can help you to tell one from another, but they aren’t conclusive. Sometimes the parent owns several classes of shares, the important ones being those with voting rights (and where it was impossible to work out an overall percentage we have tried to use these). And sometimes the percent owned is pretty meaningless – as it ranges from 0% to over 1000%!

We used the World Bank’s classification. View this classification on the World Bank website

There is no standard international definition of tax havens or secrecy jurisdictions.  For this research, we have used a list compiled by the Government Accountability Office of the United States Congress, of “Jurisdictions Listed as Tax Havens or Financial Privacy Jurisdictions.” We supplemented this with the inclusion of the Netherlands and the US state of Delaware, which are important tax havens but were not included in this list. Read the GAO report

>> Find out more on the role of the Netherlands as a tax haven
>> Find out more on the role of Delaware as a tax haven

Contrary to popular opinion, the Organisation for Economic Co-operation and Development (OECD) does not maintain a list of tax havens. A list of 'non-cooperative jurisdictions' , originally published for the London summit in 2009, is based on a narrow set of criteria and has since been updated so that only five countries are now listed as non-compliant.

An OECD report in 2000 did give a list of 40 tax havens, but this list is no longer up to date.

All of the jurisdictions on the list we have used are profiled on Financial Secrecy Index website