UPDATE: Scott Sumner one ups Arnold:
[Paul] Krugman recently announced that the sort of expert opinions I refered to are “stupid.” How does he know this? Because he looked out of the window of his train while in Rahway NJ, and things looked kind of densely populated. Something is dense, but it ain’t New Jersey. Northeast New Jersey has about 6 million people spread over a couple thousand square miles of suburbia. Paris is 20 times as dense, with 2.2 million people in an area of only 34 square miles, all living a few blocks from subway lines that will whisk them to high speed train stations. High speed rail in America? As they say in New Jersey, fugitaboutit.