For those interested in the world of non-GAAP accounting, there are a wealth of resources (particularly from the Big 4 accountancies who are eager to consult on such matters). Broadly, the use of non-GAAP has grown to a point where the SEC ramped up enforcement measures (sending letters to companies regarding their presentation of non-GAAP measures)[1]. Particularly, GAAP measures need to be presented "with equal or greater prominence" to their non-GAAP counterparts.
From a Deloitte piece[2]:
"A study published by Audit Analytics noted that 97 percent of S&P 500 companies used non-GAAP measures in earnings releases during 2017. Further, the number of non-GAAP measures used per filing has almost tripled from 2.35 in 1996 to 7.45 in 2016.
In addition, a study published by FactSet indicated that for the second quarter of 2018, 77 percent of the companies in the Dow Jones Industrial Average reported non-GAAP earnings per share and 61 percent of these companies reported non-GAAP earning per share that exceeded GAAP earnings per share."
From a Deloitte piece[2]:
"A study published by Audit Analytics noted that 97 percent of S&P 500 companies used non-GAAP measures in earnings releases during 2017. Further, the number of non-GAAP measures used per filing has almost tripled from 2.35 in 1996 to 7.45 in 2016.
In addition, a study published by FactSet indicated that for the second quarter of 2018, 77 percent of the companies in the Dow Jones Industrial Average reported non-GAAP earnings per share and 61 percent of these companies reported non-GAAP earning per share that exceeded GAAP earnings per share."
[1] https://corpgov.law.harvard.edu/2019/02/07/sec-scrutiny-of-n... [2] https://www2.deloitte.com/us/en/pages/audit/articles/a-roadm...