In the 21st century the concerns have switched to robots and artificial intelligence（AI）； 30% of American workers believe their jobs are likely to be replaced by robots and computers in their lifetime。In the past the relationship between machine and human labour has been driven by two factors：the substituting effect，which caused people to lose jobs，and the complementing effect，which allowed employees to do their work more productively。The author worries that，in the future，the substituting effect will dominate。

21世纪，人们的关切点已经转向了机器人和人工智能（AI）；30%的美国工人认为自己有生之年很可能会被机器人和计算机取代。过去，机器和人类劳动力之间的关系由两个因素驱动：一是导致人们失业的替代效应，一是让员工提高工作效率的互补效应。作者担心，在未来，替代效应将占主导。

Advances in AI have been so rapid that machines will eventually be better than people at most activities，he says，and so will be the“default choice”for performing them。A few highly paid humans will still be employed，but the rest will either struggle to find work or fall into the“precariat”，stuck in jobs that are not just poorly paid but unstable and stressful。

他认为，人工智能的进步如此之快，以至于机器最终将在大多数活动上都优于人类，因此应用人工智能将是“默认选择”。少数高收入人群仍然会有工作，但其余的人要么很难找到工作，要么沦为“朝不保夕族”，困在薪水低、不稳定、压力大的岗位上。

This gloomy view of the impact of technology is plausible。But so is a more optimistic outlook，as the economist Roger Bootle showed in“The AI Economy：Work，Wealth and Welfare in the Robot Age”，published last year。Mr Bootle argued that AI and robotics would improve productivity and economic growth， and release people from performing the most humdrum tasks。As for employment，there will always be demand for services with the human touch，just as there is an appetite for“artisanal” loaves as well as sliced white bread。

这是关于科技影响的悲观论调看似合情合理，但正如经济学家罗杰·布特尔在去年出版的《AI 经济：机器人时代的工作、健康和福利》中所展示的那样，另一种更加乐观的观点同样也不无道理。布特尔认为，人工智能和机器人技术将提高生产率和刺激经济增长，并把人们从最单调的工作中解放出来。至于就业问题，人们对人性化服务的需求总是存在的，就像除了吃切片方包，他们也要吃“手工”面包。

Which of these visions is right？Recent history has not vindicated either the optimists or the pessimists。Employment has surged in both America and Britain，suggesting that technology has not led to widespread labour replacement。

那么，种种预测中哪个是正确的呢？近期的历史并没有证明乐观主义者和悲观主义者孰是孰非。美国和英国的就业都在激增，这表明技术还没有导致广泛的劳动力替代。