(a) Labour is a factor of production that represents all human effort, both physical and mental, directed towards production while labour force refers to the employable population i e the population within the working age group who are employed plus all those who are unemployed but actively seeking work
(b) Some reasons that account for differences In earnings are;
(i) Differences in productivity among workers (II) Supply and Demand condition for skills that are relatively scarce relative to demand attract higher earnings
(iii) Working conditions. Safety, convenience, etc.
(iv) Prestige associated with Job
(v) Immobility of labour and cost of movement.
(vi) Man-made barriers e.g. trade union policies, licensing. etc
(vii) Ignorance of job opportunities
(viii) Discriminatory practices. gender discrimination.
(ix) Government policy.
(x) Natural talents e g, singers and comedians,
(xi) Cost and length of Training