Explanation:

Subsistence theories emphasize the supply aspects of the labour market while neglecting the demand aspects. They hold that change in the supply of workers is the basic force that drives real wages to the minimum required for subsistence (that is, for basic needs such as food and shelter). Elements of a subsistence theory appear in The Wealth of Nations, where Smith wrote that the wages paid to workers had to be enough to allow them to live and to support their families.

The English classical economists who succeeded Smith, such as David Ricardo and Thomas Malthus, held a more pessimistic outlook. Ricardo wrote that the “natural price” of labour was simply the price necessary to enable the labourers to subsist and to perpetuate the race. Ricardo’s statement was consistent with the Malthusian theory of population, which held that population adjusts to the means of supporting it.
Subsistence theorists argued that the market price of labour would not vary from the natural price for long: if wages rose above subsistence, the number of workers would increase and bring the wage rates down; if wages fell below subsistence, the number of workers would decrease and push the wage rates up. At the time that these economists wrote, most workers were actually living near the subsistence level, and population appeared to be trying to outrun the means of subsistence.