Remember the French HADOPI law? It did lower piracy, but it did fail to rise the sales of music and movies. Not only didn't the sales rise, but they decreased 10%. Companies often make the mistake of considering pirates their potential customers. That is false and most people wouldn't buy your product even if you offered it at ridiculously low prices. Some people pirate things because it is their only way of obtaining them.
I would say pirating does the opposite, it helps sales, there are many an album, TV show, film or any other kind of media that I wouldn't of bought if I didn't pirate it first.