What are the importance of demographic factor in marketing process?

Well, let's say your trying to sell a video game for teenagers. If you don't pay attention to Demographics, then you'll advertise to everybody, including a lot of people who have no interest in or time for Video Games. If you do pay attention to demographics, then you can advertise primarily to the teenagers. This saves a lot of money on advertising, and it makes your advertising more effective when you design ads to appeal to the particular demographic.