BEIJING — China has tightened restrictions on foreign journalists since Xi Jinping became the country’s leader four years ago, complicating efforts to parse Beijing’s thinking at a time when its slowing economy and growing global ambitions are making it increasingly important to the world.

A report released on Thursday by PEN America, a writers’ group based in New York, tries to quantify how difficult it has become for journalists to get the facts out of China. Its conclusion: The estimated 700 foreign journalists in China from 50 countries “face more restrictions now than at any other time in recent history.” The report also highlighted several instances of what it said were foreign media companies compromising editorial standards to do business in China.

The group surveyed more than three dozen journalists, as well as local Chinese employees of foreign outlets, experts, media groups and others to compile the 76-page report. PEN America has often addressed freedom of expression in China, usually concerning Chinese writers. Its executive director, Suzanne Nossel, said in an interview that it was also important to highlight challenges faced by foreigners trying to report on China.

“Of course, we can’t compare this to the pressures felt by Chinese writers,” Ms. Nossel said. “But we are dependent on the critical link that foreign correspondents play. They are an important piece of the puzzle of understanding China.”