If you run a backtest and open up details for a backtest period, the resulting chart has a column with the label "A/D". In the cases I've looked at all of the stocks in the backtest period get an "A". Be that as it may, what do "A" and "D" mean?

Thanks in advance.


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Thanks for the kind words, just back from vacation.  I am still struggling to learn like we all are.  Many databases at the consumer level have "Survivorship bias".  That means that a stock is deleted from the database when it goes bankrupt or is taken over.  It depends on your scan and how far back you go. However, you can start getting a completely different list of stocks for a given date in a backtest than you would have actually have gotten on that date.  Zacks claims to have mostly eliminated the bias.  I have been told by a Zacks representative that "D" means dead, the stock isn't around anymore.  "A" means alive, the stock is still around. 


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