U.S. Supreme Court Chief Justice John Roberts praised the often-overlooked work of federal district judges in his year-end report on the federal judiciary, avoiding any talk of politics in regards to the country's judicial system.

Incoming president Donald Trump will have more than a 100 vacancies to fill at the district and appellate court level nationwide. He'll also be able to fill the Supreme Court seat vacated following the death of Justice Antonin Scalia. The Republican-controlled Congress has refused to hold a hearing on President Obama's nominee for that empty seat.

The future of those judicial vacancies was a key issue in the presidential election.

Roberts' focus, however, was on the work of lower court judges, who he called "selfless, patriotic and brave individuals."

Congress has authorized 637 district court judgeships across the country. And the people working in those positions do so largely out of the public eye, Roberts wrote.

"You might be asking at this point why any lawyer would want a job that requires long hours, exacting skill, and intense devotion—while promising high stress, solitary confinement, and guaranteed criticism. There are many easier and more lucrative ways for a good lawyer to earn a living. The answer lies in the rewards of public service. District judges make a difference every day, and leave a lasting legacy, by making our society more fair and just," he wrote.

The report also looked at year-to-year differences in the filings brought to the federal judiciary. The most striking difference was the number of cases in which the United States was the defendant, which increased 55 percent. Roberts wrote that the increase was due to the U.S. Supreme Court's decision in Welch v. United States, which provided a new basis for certain prisoners convicted under the Armed Career Criminal Act to challenge their sentences.

Bankruptcy petitions fell to their lowest number since 2007 and the number of defendants charged with drug and immigration crimes both showed slight decreases.

Roberts wrote that the most difficult part of a judge's job is sentencing an individual who is found guilty of a crime.

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