I hope this question is allowed here, otherwise please delete it.
Currently I'm working on a historic analysis of the value investment strategy. The foundation of this work is to classify the companies into portfolios depending on the Market-to-book-value (or vice versa, doesn't matter). Within my time period of 20 years 41 companies had a negative ratio at some point. As far as I know in research such companies often get ommited. Am I right about that? 41 companies would take account for 11% of all my companies (S&P excluding non-surivivors) which seems to be a significant amount to me. If not, how would you deal with these hard to clasify companies?
Appreciate any help!