What a moment for President Obama to deliver his valedictory address to the U.N. Tuesday — defending the liberal international order at a time when it’s under severe stress around the world. Obama’s speech was preceded by some sickening reminders of how global security is fraying: The day before, a Syrian, or perhaps Russian, airstrike had ravaged a U.N. ...

  Self-driving cars got a green light from the U.S. government this week, but still have their own challenges: erratic human drivers, compromised visibility, unexpected route changes. Here’s one they won’t face until they catch on: zoning. As soon as self-driving cars are readily available, proponents will run into political battles over land use, a challenge familiar to urbanism advocates. ...

The idea that the world is awash in savings — one factor driving the theory of secular stagnation — is, on the surface, a persuasive one. Too bad it may not be true. Yes, the postwar generation is wealthier than any before it. But the ultimate value of any investment depends upon being able to convert it into cash and ...