Facts
The respondent, born in 1958, worked as a freight forwarding employee until September 2000 and registered with the IV office of the Canton of Zurich on 15 February 2001 due to a back condition that had existed since 1998. From 1 September 2001, he received a full disability pension (degree of disability 67%). Following the 4th InvIA revision, the entitlement was reduced to a three-quarter pension as of 1 June 2004. A multidisciplinary expert report by the Academy of Swiss Insurance Medicine (asim) dated 28 April 2010 confirmed a degree of disability of 67%, whereupon the IV office set a three-quarter pension.
In 2015, the IV office initiated a revision procedure ex officio after it became known that the respondent had been working as a security guard on an hourly wage basis for [D. AG] since 1 November 2011. An expert report by SMAB AG dated 28 March 2017 found a degree of disability of 10% and led to the retroactive revocation of the disability pension as of 1 November 2011 due to a breach of the obligation to report (decision dated 16 July 2018).
The respondent appealed against this decision. The Social Insurance Court of the Canton of Zurich granted him a quarter pension as of 1 April 2014 in a first judgment dated 30 September 2019, while the Federal Supreme Court quashed the judgment with its decision 8C_758/2019 dated 19 May 2020 and referred the matter back for a new decision. Subsequently, SMAB AG prepared a progress report dated 5 March 2022, which ruled out any significant change in health conditions. The Social Insurance Court of Zurich granted the respondent a graduated disability pension retroactively as of 1 November 2011 in its judgment dated 24 September 2022: three-quarter pension until 31 March 2015, quarter pension as of 1 April 2014, and half disability pension as of 1 April 2015.
The IV office of the Canton of Zurich appealed against this judgment to the Federal Supreme Court and requested that the granting of a half disability pension as of 1 April 2015 be revoked and that the pension entitlement be limited to a quarter pension until 31 May 2017. The respondent requested the dismissal of the appeal and the granting of free legal aid. The Federal Social Insurance Office waived the right to submit a statement.
Considerations
1. Examination of the right to appeal and applicable law The Federal Supreme Court examines the appeal in public law matters pursuant to Art. 95 et seq. FSCA and applies the law ex officio (Art. 106 para. 1 FSCA). It is bound by the factual findings of the lower court unless these are obviously incorrect or based on a legal error (Art. 97 para. 1, Art. 105 FSCA). The decision underlying the contested judgment was issued before 1 January 2022, meaning that the revised InvIA was not yet applicable. Therefore, the provisions of the InvIA and InvIO in the version valid until 31 December 2021 apply (intertemporal law).
2. Assessment of the prerequisites for revision A revision of the disability pension requires a significant change in the factual circumstances that is capable of influencing the degree of disability and thus the pension entitlement. This includes changes in health status as well as changes in the gainful employment effects of an otherwise unchanged health status (Art. 17 para. 1 GSSLA, Art. 7, 8 para. 1 GSSLA, Art. 4 para. 1 InvIA). A mere different assessment of an essentially unchanged factual situation is not relevant for revision purposes (BGE 144 I 103 para. 2.1).
3. Assessment of the medical expert reports and factual findings The Social Insurance Court of Zurich, following the referral by the Federal Supreme Court, obtained the SMAB progress report dated 5 March 2022. This confirmed that there had been no significant change in health conditions between the asim report dated 28 April 2010 and the issuance of the decision dated 16 July 2018. The respondent remained 100% unable to perform his original, physically demanding job, but a 60% adapted job was deemed reasonable for him. The improvement in health status alleged by the IV office could not be…