“It shows a lot of judgment to acknowledge that something that consumed a lot of resources and time did not yield the value anticipated,” Mr. Klein said. “We want agencies to be able to reflect on their collection capabilities and wind them down where appropriate. That’s the best way to ensure civil liberties and privacy are balanced with operational needs.”

In a statement appended to the report, Mr. Klein also noted that phone records were becoming less important as people shifted to using encrypted chat apps. And, he noted, the government could still gain access to some phone logs through other means, like traditional subpoenas for records of discrete accounts, or N.S.A. collection abroad, where there are fewer legal limits.

The Times reported last year that the National Security Agency had delivered a bleak internal assessment of the call records program’s steep costs and minimal benefits without taking an explicit position on whether the Trump administration should seek to extend the law that authorized it. But the specific figures undergirding that briefing were previously classified.

The privacy board, working with the intelligence community, got several additional salient facts declassified as part of the rollout of its report. Among them, it officially disclosed that the system has gained access to Americans’ cellphone records, not just logs of landline phone calls.

It also disclosed that in the four years the Freedom Act system was operational, the National Security Agency produced 15 intelligence reports derived from it. The other 13, however, contained information the F.B.I. had already collected through other means, like ordinary subpoenas to telephone companies.

The report cited two investigations in which the National Security Agency produced reports derived from the program: its analysis of the Pulse nightclub mass shooting in Orlando, Fla., in June 2016 and of a February 2016 incident in Ohio where a man attacked people at a restaurant with a machete. But it did not say whether the investigations into either of those attacks were connected to the two intelligence reports that provided unique information not already in the possession of the F.B.I.