I think that luck is of vital importance to the short story.  It is luck, a form of random selection, whereby one's name is pulled from the black box.  Something that Mr. Summers says when Tessie protests the results of the drawing.  The idea of "Everyone having the same chance" is a representation of luck.  It is this idea that ties into the theme of the short story, in that everyone has supposedly the same level of chances to being "picked."  "Luck" or this idea of being selected without much in way of individual control is of vital importance to the narrative.  Yet, where I have a challenge with the nature of the question is in the idea that "luck" is a symbol.  I think that luck is vital to the story, and something that plays a major role in both how the story advances and the thematic implications of the story.  Yet, my challenge is whether or not I can see luck as a symbol.  I don't see a particular object as being symbolic of luck or seeing luck as a symbol in the story.  Its importance is absolute and its role is extremely demonstrative.  Yet, I struggle with the idea of it being a symbol in the story.