What nation has the largest industry?

I know this may sound strange, but this question originally started out as a topic of discussion amongst me and my friends. We were discussing the social nature of ography(i.e. the conflict which exists between the legality of in certain nations and the prevalence of ography in said nations, and what this prevalence says about human nature) and I started to wonder which nation actually had the largest industry. If, when answering, you could cite the sources for your information, I would be most appreciative. And please, no suppositions.