Survivorship bias: the list you see is the winners

survivorship bias

Testing on names that exist today: every index list, screen result and price database defaults to the survivors - the delisted, acquired and bankrupt have left the file. A strategy backtested on today's members was tested on companies certified, by survival itself, to have done well - and its results inherit that certification as phantom edge. The equity-specific data trap, and the reason point-in-time membership is non-negotiable.