The review, prepared for the New Zealand Treasury by Willis Towers Watson, said the Guardians of New Zealand Superannuation, the Crown entity that manages the fund, was a global best-practice organisation and effective in carrying out its mandate.

Overall Willis Towers Watson found the Guardians was “best-practice in its activities and more capable of achieving high performance than the vast majority of its peers.” It described the Guardians’ governance model as “exceptionally strong” and its investment approach and returns as “very impressive”.

Chair Catherine Savage said the Guardians’ board was proud of the review. “We aim to be world class in everything we do and it is incredibly affirming to hear that we are indeed performing at global best practice level. We take our mission to be the kaitiaki / guardians of the investment New Zealanders are making in the fund very seriously.”

The report said responsible investment was a rapidly developing area of investment practice that was set to become increasingly mainstream. It found the Guardians’ approach to responsible investment to be impressive and said there was a need to continue to evolve and innovate to maintain the fund’s leadership position in the area, for which more resource would be needed in the future.

The Guardians are required by legislation to undergo an independent review every five years.