Footnotes

• Contributors CO and DJ conceived the idea. AW, CP, VA and CO led the exercise, and CO and VA gathered the results. VA took the lead in organising the data and writing the manuscript. CO edited the manuscript. All authors reviewed the manuscript and agreed with the final product.

• 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.

• Disclaimer The views expressed in this article reflect the results of research conducted by the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense or the US Government.

• Competing interests None declared.

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

• Author note I am a military service member. This work was prepared as part of my official duties. Title 17 U.S.C. 105 provides that “Copyright protection under this title is not available for any work of the United States Government.’ Title 17 U.S.C. 101 defines a United States Government work as a work prepared by a military service member or employee of the United States Government as part of that person’s official duties.