This story hints at a general principle: the experience of waiting, whether for luggage or groceries, is defined only partly by the objective length of the wait. “Often the psychology of queuing is more important than the statistics of the wait itself,” notes the M.I.T. operations researcher Richard Larson, widely considered to be the world’s foremost expert on lines. Occupied time (walking to baggage claim) feels shorter than unoccupied time (standing at the carousel). Research on queuing has shown that, on average, people overestimate how long they’ve waited in a line by about 36 percent.