CUME_DIST
Shows the share of rows that come before the current one or tie with it — from 0 to 1.
Syntax
CUME_DIST() OVER (ORDER BY <sort key>)
CUME_DIST() OVER (PARTITION BY <group> ORDER BY <sort key>)
Calculates (rows up to the current one, ties included) / (all rows). Unlike PERCENT_RANK, it never gives 0: the first row gets at least 1 / count, and the last always gets 1. Handy for phrases like “80% of people earn the same or less”.