The Economics of Immigration in One Lesson

Or perhaps I should say in one equation properly explained . . .

Political thinking: 

    ALL THE STUFF divided by ALL THE WORKERS equals STUFF PER WORKER

The implication of this is more workers means less stuff for workers.

Economic thinking: 

    ALL THE WORKERS multiplied by STUFF PER WORKER equals ALL THE STUFF

The implication of this is more workers or more productivity means more stuff for workers.

Definitions: 

All the stuff = production, the output;

all the workers = resources, the input; 

stuff per worker = productivity, the rate at which we can produce stuff

Allowing more workers (immigration as well as the removal of barriers to entry like licensure laws and minimum wages) is clearly a net good when total output rises. 

The key to consumption is production. The key to mass consumption is mass production.*

(HT: Bryan Caplan)

*Note for minimalists, environmentalists, etc.: Don't get hung up by the term "mass" here. This does not mean "excessive". It means flourishing for the masses. Limitations on production/consumption hit the worst off first and the best off almost never.