Opinion of the Court
existed in the national economy. See ibid.
On cross-examination, Biestek’s attorney asked O’Callaghan “where [she was] getting those [numbers] from.” Id., at 71. O’Callaghan replied that they came from the Bureau of Labor Statistics and her “own individual labor market surveys.” Ibid. The lawyer then requested that O’Callaghan turn over the private surveys so he could review them. Ibid. O’Callaghan responded that she wished to keep the surveys confidential because they were “part of [her] client files.” Id., at 72. The lawyer suggested that O’Callaghan could “take the clients’ names out.” Ibid. But at that point the ALJ interjected that he “would not require” O’Callaghan to produce the files in any form. Ibid. Biestek’s counsel asked no further questions about the basis for O’Callaghan’s assembler and sorter numbers.
After the hearing concluded, the ALJ issued a decision granting Biestek’s application in part and denying it in part. According to the ALJ, Biestek was entitled to benefits beginning in May 2013, when his advancing age (he turned fifty that month) adversely affected his ability to find employment. See App. to Pet. for Cert. 19a, 112a–113a. But before that time, the ALJ held, Biestek’s disabilities should not have prevented a “successful adjustment to other work.” Id., at 110a–112a. The ALJ based that conclusion on O’Callaghan’s testimony about the availability in the economy of “sedentary unskilled occupations such as bench assembler [or] sorter.” Id., at 111a (emphasis deleted).
Biestek sought review in federal court of the ALJ’s denial of benefits for the period between October 2009 and May 2013. On judicial review, an ALJ’s factual findings—such as the determination that Biestek could have found sedentary work—“shall be conclusive” if supported by “substantial evidence.” 42 U. S. C. §405(g); see supra, at 1. Biestek contended that O’Callaghan’s testimony could
