Brought out of the dark depths of the United Nations Millenium Development Goal (UNMDG), the call is out for a billionaire's tax. It's been on paper for years now, but few believe it. The United Nations on Thursday called for a tax on billionaires to help raise more than $400 billion a year for poor countries. An annual lump sum payment by the super-rich is one of a host of measures including a tax on carbon dioxide emissions, currency exchanges or financial transactions proposed in a UN report that accuses wealthy nations of breaking promises to step up aid for...