“This focus on cities as the true engines of economics neatly explains both eurozone and pre-euro failures. European national currency zones were already too big – the eurozone made something already oversized even worse. The US is rich despite having one currency, and it suffers huge damaging cycles from being locked into that single currency zone. Long protected by exceptional rates of internal labour mobility (three times the rate within France), there are signs that US labour mobility is slowing, and a dollar-bloc handicap is becoming more visible.”