By now, anyone following the Democratic Presidential nomination has heard a great deal about so-called "green-collar" jobs. Barack Obama has promised five million new jobs in fields such as renewable energy. Hillary Clinton has displayed similar enthusiasm.

Are these promises for real?

The environmental magazine Grist provides a nice overview this morning. But even Grist seems to be struggling to get its facts straight. The UT-Rand Corporation study it cites in support of the proposition that a new focus on renewable energy could generate five million jobs seems to have been withdrawn.

So for now, anecdotes are all we have.