The criteria for membership in the Commonwealth of Nations, which apply to current and prospective member states, have been altered by a series of documents issued over the past eighty-two years. The most important of these documents were the Statute of Westminster (1931), the London Declaration (1949), the Singapore Declaration (1971), the Harare Declaration (1991), the Millbrook Commonwealth Action Programme (1995), the Edinburgh Declaration (1997), and the Kampala Communiqué (2007). New member states of the Commonwealth must abide by certain criteria that arose from these documents, the most important of which are the Harare principles and the Edinburgh criteria.