The constituency of the parliament is based upon the islands of Tuvalu. The larger islands elect two members, while Nukulaelae elects one member. The smallest island, Niulakita, is represented in the parliament by the members of the constituency of Niutao. A candidate for parliament must be a citizen of Tuvalu of a minimum age of 21 years. Voting in Tuvalu is not compulsory. At 18 years of age, Tuvaluans are eligible to be added to the electoral rolls. At the date of independence there were 12 members of the parliament. The Electoral Act was amended in December 1999 to increase the membership of parliament from 12 to 15 MPs. In August 2007 the Constitution was changed to increase the number of ministers from 5 to 7. Those members selected the Prime Minister and the Speaker of the parliament by secret ballot. The Ministers that form the Cabinet are appointed by the governor-general on the advice of the prime minister. The Attorney-General sits in parliament, but does not vote, as the parliamentary role of the Attorney-General is purely advisory.