last season, 17th and 18th had 28 points and joint -19 GD after 30 games, when 37 points was enough for 17th place (18th had 36).
This season, us and Wigan may be joint 30 points after 30 games, so it looks like a projected 38-39 points could be needed.
I think Wigan will escape again, but Sunderland will go down.