Theory about guardian selection

after doing some thinking, and reading the lore about shin malphur, i’ve come to the conclusion that ghosts tend to choose dead people as guardians purely because there are more viable candidates. think about it: assume the city has a population of 50 million (which is bigger than many countries, but i’m going for an optimistic approach) and earth had 10 billion people on it at the time of the collapse, then the odds of a given candidate being dead is 200:1, or 0.5%. if we then expand to the fact that ghosts can resurrect people from every planet, and we assume that every other planet combined also has a total of 10 billion, giving a total human population circa the collapse of 20 billion, the odds of a candidate being alive drops to 0.25%, or 1 in 400. also acknowledging the fact that those alive in the golden age were touched by the light, thew were more likely to be viable candidates. is there anything that could disprove this theory?