Associate Justice of the Supreme Court of the United States is the title of all members of the Supreme Court of the United States other than the chief justice of the United States. The number of associate justices is eight, as set by the Judiciary Act of 1869. Article II, Section 2, Clause 2 of the United States Constitution grants plenary power to the president to nominate, and with the advice and consent (confirmation) of the Senate, appoint justices to the Supreme Court. Article III, Section 1 of the Constitution effectively grants life tenure to associate justices, and all other federal judges, which ends only when a justice dies, retires, resigns, or is removed from office by impeachment. Each Supreme Court justice has a single vote in deciding the cases argued before it; the chief justice's vote counts no more than that of any other justice. However, the chief justice—when in the majority—decides who writes the court's opinion. Otherwise, the senior justice in the majority assigns the writing of a decision. Furthermore, the chief justice leads the discussion of the case among the justices. The chief justice has certain administrative responsibilities that the other justices do not and is paid slightly more ($267,000 per year as of 2018, as opposed to $255,300 per year for each associate justice). Associate justices have seniority by order of appointment, although the chief justice is always considered to be the most senior. If two justices are appointed on the same day, the older is designated the senior justice of the two. Currently, the senior associate justice is Clarence Thomas. By tradition, when the justices are in conference deliberating the outcome of cases before the Supreme Court, the justices state their views in order of seniority. The senior associate justice is also tasked with carrying out the chief justices's duties when he is unable to, or if that office is vacant. Historically, associate justices were styled "Mr. Justice" in court opinions and other writings. The title was shortened to "Justice" in 1980, a year before Sandra Day O'Connor became the first female justice.