Nuclear Weapons Proliferation - A Chain Reaction

William Broad was giving a review of two books on nuclear weapons history in the NY Times about a month ago. I stumbled upon the report from another blog. The books, eh, I can take or leave.

The graphic, however, is interesting. It shows the connections on how other nations developed their nuclear weapons capabilities - and, of course, it all started with the United States. The question is, who's the next state? Or better yet, what's stopped them from becoming nuclear powers before today? Maybe they're just not interested in the hassle of managing this capability.