I wonder how everyone handles missing data during strategy development. Here, I mostly refer to the EOD close data that is missing due to the fact that the company is delisted, not listed yet, or simply not trading for a period of time. I have seen some quant researchers recommend forward filling the missing data first, then backfilling. However, to me it makes more sense to fill the missing price data with 0s. This way I can tell my algorithm to exclude those 0-priced tickers from the trading universe. So, if I am not holding such tickers, I would not be able to open positions in them. And if I have positions open then I would not be able to close / alter them. I will also incur a 100% loss on those positions (100% gain on shorts) that is either temporary, or permanent depending on if it is a delisting, or a halt. Does this approach make sense? Is there a reason why forward-filling / back-filling is preferable to the 0-fill? Is there another way to handle missing data I am not aware of? Thank you.