The Government of Singapore operates under a Westminster parliamentary system defined by the Constitution to consist of the President and the Executive. Executive authority is vested in the President but exercised on advice of the Cabinet led by the Prime Minister. The President acts as Head of State with certain discretionary powers including appointing the Prime Minister and withholding parliamentary dissolution, while the Cabinet heads the Executive through 16 ministries and statutory boards. Since achieving full internal self-government in 1959 and independence in 1965, the People’s Action Party has continuously formed the government. Singapore employs a parliamentary democracy with general elections held at least every five years, though critics have raised concerns about restrictions on political opposition and press freedom.