When an agency adopts a new interpretation of a statute and rejects an old interpretation of the statute?

Even when an agency adopts a new interpretation of a statute and rejects an old, a court must continue to apply a deferential standard of review: "When [the agency] does [change its mind], the courts still sit in review of the administrative decision and should not approach the statutory construction issue de novo and without regard to the administrative understanding of the statutes." (NLRB v. Iron Workers, supra, 434 U.S. at p. 351, 98 S.Ct. at p. 661.)