Out of the 20 (some sources say there were 19) kings of the Northern Kingdom of Israel, there were zero good kings.
Out of the 20 kings of the Southern Kingdom (Judah), there were eight good kings. (Not perfect, just good. Still sinners.)
That's one in five.
(My info is from my study Bible and something I remember from the Walk Thru the Old Testament seminar our family took years ago.)