David Card is the author of a study that purports immigration has almost zero effect on the wages of domestic low-skilled workers. Wages could remain untouched if (within the bounds of realistic immigration rates) labour demand is elastic. That means that as the supply of workers increases, wages stay the same because employers want to hire more people. The contradiction lies in David Card’s legendary study with Paul Krueger arguing minimum wage doesn’t reduce employment. For this to be true, demand would have to be inelastic. Meaning, that even as employees become more expensive, companies need to hire the same number of people: no fewer than before. Both cannot be true. My bias tells me that if I had to say which is more plausible, it would be his finding about immigration. The demand for a good is inelastic when there is no good substitute or if the expense is minimal relative to total spending. In the case of low-skilled labour, neither holds up: workers are eminently replaceable by machines, and labour is usually the costliest part of any business.