Its effectiveness is determined by the arrangement of elements. Inevitably, these elements are viewed in some kind of hierarchical fashion, with some elements having more importance than others. Other factors influence design that don't have the same implications in art. Visual movement plays a significant part in the effectiveness of the design, while it's not as fundamental to art. The placement and interpretation of written content assumes an importance in graphic design not found in painting and sculpture.
Art can be static and still be effective.
Design invariably prompts visual movement. The external associations of written content assume major importance in design. We look at it formally, viewing it as an artistic form. If we view the same oversize letter in a full-page ad in the local newspaper, we begin searching for some kind of verbal explanation or guide to help us understand what literal meaning that letter might have. In design, the literal meaning of the words assumes a major importance in determining the effectiveness of the piece.