Footnotes

• Twitter @morgancarpenter, @kbdalke, @briandavidearp

• Contributors BDE wrote the first draft based on conversations with KD and MC. MC and KD contributed substantial writing and editing. All authors then further revised and approved the final version.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests None declared.

• Provenance and peer review Not commissioned; internally peer reviewed.