Or perhaps it's simply an empirical measure of the typical ratio of known to unknown in software engineering: 1:2. It can be used as a heuristic to accommodate

Or perhaps it's simply an empirical measure of the typical ratio of known to unknown in software engineering: 1:2. It can be used as a heuristic to accommodate for the fact that we have biases and can't predict everything, but the industry as a whole has found a way around that.