In his 1968 paper, Altman found that sales volume (i.e., sales divided by total assets) is a useful predictor not by itself, but as a suppressor variable to improve the predictive power of EBIT/TA.
Suppressor variables are such that they do not or not significantly correlate with the dependent variable, but they do have a high (positive or negative) correlation with another independent variable.
In this case, Altman found a high negative correlation between sales volume and EBIT in the bankrupt sample. All other things being equal, this would imply that companies go bankrupt when they sell their wares at a higher profit margin?
I've been racking my brain as to why that is.
Altman's 1968 paper: https://pdfs.semanticscholar.org/cab5/059bfc5bf4b70b106434e0cb665f3183fd4a.pdf