At the national level, Argentina elects a head of state (the President) and a legislature. The franchise extends to all citizens aged 16 and over, and voting is mandatory (with a few exceptions) for all those who are between 18 and 70 years of age. The President and the Vice-President are elected in one ballot, for a four-year term, by direct popular vote, using a runoff voting system: a second vote is held if no party wins more than 45% of the votes, or more than 40% with also at least 10 percentage points more than the runner-up. Before the 1995 election, the president and vice-president were both elected by an electoral college. The National Congress (Congreso Nacional) has two chambers. The Chamber of Deputies of the Nation (Cámara de Diputados de la Nación) has 257 members, elected for a four-year term in each electoral district (23 Provinces and the Autonomous city of Buenos Aires) by proportional representation using the D'Hondt method, with half of the seats renewed every two years in all districts. The Senate of the Nation (Senado de la Nación) has 72 members, elected for a six-year term in three-seat constituencies (23 provinces and the Autonomous city of Buenos Aires) for a six-year term, with two seats awarded to the largest party or coalition and one seat to the second largest party or coalition. One-third of the constituencies are renewed every two years. In 2001 the whole senate was renewed. A gender parity law, adopted in 2017, mandates that party lists must alternate between male and female candidates. History Universal, secret and compulsory voting for male Argentine citizens, either natural-born or naturalized, was guaranteed by the 1912 Sáenz Peña Law, named after President Roque Sáenz Peña. The first free elections under the Sáenz Peña regime were held in 1916. Women did not have the right to vote in Argentina until 1947, when Law 13.010 ("on political rights for women") was sanctioned during the government of Juan Domingo Perón. Women first voted in a national election in 1951. Throughout the 20th century, voting was suppressed by Argentina's numerous dictatorial regimes. The dictatorships of José Félix Uriburu (1930–1932) and the so-called Revolución Libertadora and Revolución Argentina, as well as the last military dictatorship (1976–1983), all suppressed voting altogether. In addition, electoral fraud was widespread under the successive governments of the so-called Infamous Decade. Since the return of democracy in