McDonald’s has always been predominantly staffed by the young. Those who are filling part-time jobs flipping burgers to make some money in between classes. But that could soon change, given the results of a recent British survey. After reviewing the performance of 400 McDonald’s franchises in Britain, Lancaster University Management School found that customer satisfaction was 20 percent higher at stores with some workers over the age of 60. McDonald’s says that the experience, work ethic and people skills of older workers is behind the boost in profit at those stores. One company official said McDonald’s would like to add more 60-plus workers. But it won’t be easy. The over-60 set represents only about one per cent of McDonald applicants.