The Modern Slavery Act 2015 requires companies that trade in the UK with a turnover of £36 Million or greater to publish a statement on their website detailing the steps they are taking to ensure that slavery and human trafficking are not taking place in the business (or its supply chains).
This metric is being used to research whether relevant companies have published such a statement on their website. Collecting these statements is the first step in a project to investigate what companies are doing to combat slavery - the next step will be to analyse the content of these statements.
As companies are directed to publish these statements "on their own website" there is no single repository where these statements can be accessed (this metric will serve as such a repository).
The Business & Human Rights Resource Centre are maintaining a list of the statements that they're aware of - this is a great resource and should probably be the starting-point to check if the company you're researching has published a statement.
Other than this, the best method I have found for sourcing statements thus far is simply to search for "[Company name] modern slavery statement".
If you come up with additional ways to locate these statements please leave a comment or edit this methodology section directly.
If you can't find this kind of statement for a company, set the value to "No" with a "Report" source describing the steps you took to try and find the statement. Set the "year" for this value as the previous year (the company may still release a statement that covers the current year).