[atlantic]

Well, microeconomic theory is not that complicated either. If you take a particular labour market, and increase the supply, the point of equilibrium for wages shifts downwards. The magnitude of the shift depends on the elasticity of demand. If demand is fairly static, as is the case for basic services such as plumbing, then the shift in wages will be large.

Now, the question of immigration is not just about economics. It's a political question, so other factors come into play. But as far as the economic part is concerned, there is no question that substantial immigration depresses wages in specific labour markets.