Human capital is the stock of expertise accumulated by a worker to enhance future productivity.

Firm-specific skills raise a worker’s productivity only if he or she works for that particular firm.

General skills enhance productivity in many jobs, not just the current one.

Signalling is the decision to undertake an action in order to reveal inside information.

Screening is the process of learning inside information by observing differences in behaviour.

Discrimination is the different treatment of people whose relevant characteristics are identical.

A closed shop is an agreement that all a firm’s workers will be members of a trade union.