The comics industry experienced a brief boom in the early 1990s, thanks to a combination of speculative purchasing (mass purchase of the books as collectible items, with intent to resell at a higher value as the rising value of older issues, was thought to imply that "all" comics would rise dramatically in price) and several storylines which gained attention from the mainstream media. DC's extended storylines in which Superman was killed, and superhero "Green Lantern" turned into the supervillain Parallax resulted in dramatically increased sales, but the increases were as temporary as the hero's replacements. Sales dropped off as the industry went into a major slump, while manufactured "collectables" numbering in the millions replaced quality with quantity until fans and speculators alike deserted the medium in droves.