Will robots displace humans as motorised vehicles ousted horses?

IN THE early 20th century the future seemed bright for horse employment. Within 50 years cars and tractors made short work of equine livelihoods. Some futurists see a cautionary tale for humanity in the fate of the horse: it was economically indispensable until it wasn’t. The common retort to such concerns is that humans are far more cognitively adaptable than beasts of burden. Yet as robots grow more nimble, humans look increasingly vulnerable. A new working paper concludes that, between 1990 and 2007, each industrial robot added per thousand workers reduced employment in America by nearly six workers. Humanity may not be sent out to pasture, but the parallel with horses is still uncomfortably close.

Robots are just one small part of the technological wave squeezing people. The International Federation of Robotics defines industrial robots as machines that are automatically controlled and re-programmable; single-purpose equipment does not count. The worldwide population of such creatures is below 2m; America has slightly fewer than two robots per 1,000 workers (Europe has a bit more than two). But their numbers are growing, as is the range of tasks they can tackle,...