My impression is that most people in the 1700s would believe in ghosts haunting houses, but that most people today would not. When did that change? In particular, during the 1960s when there were many government funded psychadelic experiments, would the average American have believed in ghosts?
https://www.ipsos.com/en-us/news-polls/majority-americans-believe-ghosts-57-and-ufos-52
This is from 2008. I went with it because it's Ipsos/McClatchy and therefore more scientific. But you can Google lots of more recent results on other sites that indicate this hasn't changed much.
57% of Americans believed in ghosts in 2008. I'm not sure there has ever been a point when a majority of Americans DIDN'T believe in ghosts. There may have been a time when a majority didn't believe in ghosts, but polling only goes back to the FDR years.