Statistics from Altmetric.com
Contributors NW and JM independently initiated the project and then worked together. JM obtained the data, which were analysed by NW. All authors contributed to the preparation of the manuscript.
Funding Health Research Council of New Zealand.
Competing interests None.
Ethics approval The study was exempt from ethical review as it involved the use of existing collections of secondary non-identifiable data.
Provenance and peer review Not commissioned; internally peer reviewed.
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