I am building a methodology to measure the activity of companies on several management areas represented on a radar chart from annual accounting information of financial statements. You can get it from Google several manuscripts of this new methodology and it can be apply according your need of research.
The next manuscript is an example:
Comparative analysis of enterprises of covering floors and walls by applying the radar charts methodology
You can use Wilcoxon signed rank test to measure the indices before and after the recovery periods. Take indices when the company was in decline, similarly take the indices after recovery, analyse the data using the Wilcoxon signed rank test