The Economist does a service to all of us (definitely includes this humble scribe) who have no inclination to read Piketty’s book but want the simple, nail-the-essence summary of what’s going on. Your link is here, well worth five minutes of your time to get a handle on what all the fuss is about.
And r>g makes perfect sense because round these parts it stares at you in the face 24/7. Great marketing too, up there with emc2, snowball earth or selfish gene.