"In the end, the team's conclusions do not mean that humanity is alone in the universe, or that the odds of finding evidence of extra-terrestrial civilizations (both past and present) is unlikely. Instead, it simply means that we can say with greater confidence – based on what we know – that humanity is most likely the only intelligent species in the Milky Way Galaxy at present."
Read more at:
https://phys.org/news/2018-06-advanced-civilization-universe.html#jCp
Fun, quick read.-WW
ps. Doesn't factor ghosts and such but has some maths on why we haven't found ET's yet.