White Dragon as a Zero  (Article ID 104)

Abstract:  The White Dragon (Soap) was chosen to represent a zero because it is a blank tile. Since blank is equivalent to nothing, it is considered to be a zero. This ruling is not found in Mah Jongg Made Easy.

Question from a player:  Why is a White Dragon used as a zero? 
 
Answer from the NMJL:  “Our reasoning, White Dragon is a blank tile.  Blank is nothing and nothing is zero.  When used as a zero it has no matching suit.  Only a joker can be used in its place.”  
 
Source: Mah Jongg Made Easy (not included); National Mah Jongg League Bulletin Q&A (1981 page 5, 2000 page 5) https://www.nationalmahjonggleague.org