Immigration Policy Impacts Labour Supply

Steps:

• Define labour force as the total number of people available and willing to work in an economy.
• Identify factors influencing size: population growth, migration, participation rates, and age demographics.
• Evaluate each option against these factors to see direct effects on quantity of workers.
• Select the option that directly alters the pool of potential workers.

Why B is correct:

• Labour force size is determined by the working-age population; immigration policy controls inflows of foreign workers, directly expanding or contracting this population per economic definitions of labour supply.

Why the others are wrong:

• A: Trade unions influence wages and conditions but not the total number of workers.
• C: Quality of graduates affects productivity and skills, not the quantity in the labour force.
• D: Male-female ratio impacts composition but assumes fixed total employees, not size.

Final answer: B