Amid a busy few weeks for restaurant earnings, new data is emerging that suggests a restaurant recession could be underway. The pullback is most marked among the young customers who have long propped up the boom in “fast-casual” restaurants — chains built on recognizable ingredients, counter service, and prices roughly 50% higher than fast food. Shares of Chipotle fell some 5% last week after the chain's earnings report showed that margins fell and comparable-store sales growth appeared barely positive. S ...