NEW YORK ( TheStreet) -- Halloween isn't just for kids anymore. The haunted attraction industry is approximately $300 million in size with an estimated 2,500 attractions worldwide, according to the Haunted Attraction Association . If you include major amusement theme parks that operate a haunted event, that number rises to between $400-$500 million, says Larry Kirchner, editor-in-chief of HauntWorld.com. "If you add up ticket sales and the value of professional effects and vendors involved in the haunted attraction industry, it averages as an industry at $1 billion per year," Kirchner says. Even though it's a small portion of the overall $8 billion Halloween industry, the numbers are impressive given that haunted theme parks and the wide variety of hayrides, corn mazes, haunted houses and the like only operate for less than two months out of the year. Shocktoberfest in Reading, Pa., says at just 25 years old, the Halloween entertainment industry is still relatively young. The industry has evolved from hayrides and outdoor walkthroughs to large scale animatronics, special effects, make-up and costumes. "All of that makes up our industry today," Konopelski says. With 300 members, the Haunted Attraction Association's mission is to promote a network of haunted attractions including haunted houses, hayrides, historical sites and other supernatural experiences. The association also advises the industry on haunt safety standards to protect customers. The haunted attraction industry got its beginnings in the non-profit sector. When it became apparent that consumers wanted more Halloween-themed entertainment and were willing to pay for it, "that's when the entrepreneurs stepped in," Konopelski says. "People that had facilities, either farms or property that they could use for these events, they started making investments. As the industry evolved then we started seeing the vendors that made stuff and some vendors were already making it like skeleton companies," he says.