If the technological revolution continues to have its effects, there will be fewer and fewer jobs available, particularly to school-leavers and those over the age of fifty．If there are only half the number of jobs in the future, men and women will have to share them．Two people will therefore work only twenty hours each instead of the forty they are currently accustomed to．It is a well-known fact that those who suffer from stress at work are often not high-powered executives but unskilled workers doing boring, repetitive jobs, especially those on production lines．Unemployment often has a similar effect on its victims．If we wish to pr this type of stress and the depression(沮丧)that frequently follows long periods of it, we will have to find ways of educating people to cope with this sudden increase in leisure time．Many have already turned to pills and tablets to combat sleeplessness and anxiety, two of the symptoms of long-term stress and depression．In America, we spend $ 650 million a year on different kinds of medicines．We swallow a staggering(大得惊人的)three million sleeping tablets every night．Although these 'drugs of the mind' can be extremely useful in cases of cr, the majority of patients would be better off without them．The boredom and frustration of unemployment are not the only causes of stress: poor housing, family problems, overcrowding and financial worry are all significant factors．Nevertheless, doctors believe that if people learnt to breathe properly, took more exercise, used their leisure time more actively and expressed their anger instead of bottling it up, they would not depend so much on drugs, which treat only the symptoms and not the cause of the stress．If doctors refused prescriptions more often and discouraged patients with minor ailments from visiting the clinic, the country would have more money to spend on improving leisure facilities and education, which are at present inadequate in many parts of the country．Moreover, doctors would have more time to spend on those patients in real need of their help．Questions:
During which period could British motorists drive without speed limits?