The idea of ghosts and spiritual beings often automatically instill fear in some people, but this need not be the case. If ghosts do indeed exist then there would still be no need to fear them, at least not any more than any living entity. If ghosts are rational economic actors then ghosts would have no incentive to severely disturb the living population as it is likely that the costs to the ghost of killing an individual outweigh the benefits. When a ghost kills an individual then that individual could then conceivably turn into a ghost and, as a ghost, annoy its phantom killer for an even longer time period than if left alive...
That is the abstract of Rational Ghost: Using Basic Economic Principles to Explain Ghost Behavior. Apparently, even ghosts follow the logic of homo economicus.
The implication? You should look to purchase a house that is believed to be haunted. The paper reports that haunted houses sell for about 3 percent less than the average, yet ghosts don't carry any cost. Or something like that.
(Hat tip: The Perfect Substitute)