I am quite new to studying finance so apologies if this turns out to be a trivial question. I am writing my first essay where I want to test a value strategy from 2009-2019 by yearly ranking of the stocks by their P/CF ratio, forming 5 portfolios, evaluating their performance.
Regarding survivorship bias, I understand that it is necessary to consider the members of the index in each year under analysis (i.e. for the holding year 2009 - 2010, the index constituents per 2009 are to be considered) But I am unsure if 2009 as a starting year would cause issues, meaning that only the survivors of the market crash are considered. Do you see any issue with this or am I making a thinking error?
Thank you for your help.