As professional boxing has four major sanctioning bodies (WBA, WBC, IBF, WBO) each with their own champions, the sport doesn't have a centralized ranking system.
The rankings published by these organizations share the trait of not ranking the other organizations' champions, as each one of the sanctioning bodies expects their champion to frequently defend their title against their top-ranked contender.
The IBF's protocol is for the top 2 spots in its rankings to remain vacant until two of its other top-ranked contenders face off, at which point the winner takes one of those two places.
The aim of both the TBRB and The Ring is to crown a single champion for each division.
Since the 90s, other parties have experimented with objective computerized rankings, but these are sometimes regarded as incapable of accounting for all of boxing's quirks and subtleties.