First, the average tenure of a justice is much longer now. From 1941 to 1970, justices served an average of about 12 years. But from 1971 to 2000, they served an average of 26 years.

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That figure has increased only since 2000. When John Paul Stevens retired from the court in 2010, he had served 35 years. When Antonin Scalia died, he had served 30 years. Anthony M. Kennedy has served 29 years, Clarence Thomas 26 years, Ruth Bader Ginsburg 24 years, and Stephen G. Breyer 23 years. Presidents who might serve only four years can have influence decades later if they can appoint someone to the Supreme Court.

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Second, precisely because justices serve so much longer, vacant seats arise less often. From 1881 to 1970, a vacancy arose on average once every 1.7 years. But since 1970, a seat has become vacant only once every three years or so. In the first era, a two-term president typically would appoint four or five justices, or more than half the court. But since 1970, a two-term president would typically appoint two or three justices.

The longer period between vacancies also means that some presidents will not appoint any Supreme Court justices at all. Jimmy Carter was the first president to complete one term without having made a single appointment. If George W. Bush had been a one-term president, the same would have happened to him.

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Here’s another way to express the changing nature of the court. From 1994 to 2005, the court had gone nearly 11 years without a vacancy — the longest period since its size became fixed at nine justices in 1869. Similarly, three of the five longest stretches between vacancies since 1869 have occurred in the past 30 years.

Third, the power of the Supreme Court has increased significantly. Over the 20th century, the court became more aggressive in declaring federal and state legislation unconstitutional. In the 1940s and 1950s, the court was invalidating about one act of Congress each year. In the 1990s, that number had become about four a year. Since 2010, it has been about three per year. And a bare count of numbers can’t capture the significance of key decisions: A decision that strikes down state laws that deny same-sex marriage has far greater resonance than a decision that strikes down one particular economic regulation.

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Most of the work of the court, however, does not involve constitutional rulings but the interpretation of federal statutes. Here, current circumstances also make the court more powerful. In theory, when the court interprets a federal law, Congress can always step back in and reject its interpretation. But in our era of polarized and fragmented political parties, the court’s word is more often the last word. Congress is frequently too divided and paralyzed to reject the court’s interpretations of federal law.

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Finally, the court is more powerful because political actors and the rest of us abide by its decisions, in a way that could not always be taken for granted in the past. In the early 20th century, Justice Oliver Wendell Holmes said that anything the court tried to do about the massive disenfranchisement of black voters in the South “would be an empty form” with little more effect than “a name on a piece of paper.” Fearing that any order it issued would simply be ignored in the South, the court refused to act.

Yet by 1954, the court was prepared to hold segregation unconstitutional in the famous in Brown v. Board of Education decision. By 2000, the court was able to resolve a disputed presidential election with security that its decision would be honored.

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The Supreme Court confirmation wars will become less heated only if the stakes in individual appointments diminish. One way to bring that about would be a constitutional amendment limiting Supreme Court terms to 18 years, staggered so that vacancies would occur at regular two-year intervals. Academic authorities on the Court and others have been floating versions of such proposals for years, but they have gotten little political traction. Absent change of this sort, the confirmation wars are likely to grow hotter.

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Richard H. Pildes is Sudler family professor of constitutional law at New York University and author of “Is the Supreme Court a ‘Majoritarian’ Institution,” from which the data here are drawn.