Lewis's Dual Sector Model of Development: The theory of trickle down
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Lewis proposed his dual sector development model in 1954. It was based on the assumption that many LDCs had dual economies with both a traditional agricultural sector and a modern industrial sector. The traditional agricultural sector was assumed to be of a subsistence nature characterised by low productivity, low incomes, low savings and considerable underemployment. The industrial sector was assumed to be technologically advanced with high levels of investment operating in an urban environment.
Lewis suggested that the modern industrial sector would attract workers from the rural areas. Industrial firms, whether private or publicly owned could offer wages that would guarantee a higher quality of life than remaining in the rural areas could provide. Furthermore, as the level of labour productivity was so low in traditional agricultural areas people leaving the rural areas would have virtually no impact on output. Indeed, the amount of food available to the remaining villagers would increase as the same amount of food could be shared amongst fewer people. This might generate a surplus which could them be sold generating income.
Those people that moved away from the villages to the towns would earn increased incomes and this crucially according to Lewis generates more savings. The lack of development was due to a lack of savings and investment. The key to development was to increase savings and investment. Lewis saw the existence of the modern industrial sector as essential if this was to happen. Urban migration from the poor rural areas to the relatively richer industrial urban areas gave workers the opportunities to earn higher incomes and crucially save more providing funds for entrepreneurs to investment.
A growing industrial sector requiring labour provided the incomes that could be spent and saved. This would in itself generate demand and also provide funds for investment. Income generated by the industrial sector was trickling down throughout the economy.
Problems of the Lewis Model
- The idea that the productivity of labour in rural areas is almost zero may be true for certain times of the year however during planting and harvesting the need for labour is critical to the needs of the village.
- The assumption of a constant demand for labour from the industrial sector is questionable. Increasing technology may be labour saving reducing the need for labour. In addition if the industry concerned declines again the demand for labour will fall.
- The idea of trickle down has been criticised. Will higher incomes earned in the industrial sector be saved? If the entrepreneurs and labour spend their new found gains rather than save it, funds for investment and growth will not be made available.
- The rural urban migration has for many LDCs been far larger that the industrial sector can provide jobs for. Urban poverty has replaced rural poverty.
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Related Glossary Items:
Rural Urban Migration
Industrialisation of Zambia
Low Productivity of Traditional Farming Methods
Fisher Clark's Theory of Structural Change
The Harrod-Domar Model
Rostow's Model - the Stages of Economic Development
Models of Demographic Transition
The Causes of Economic Growth
Supply Side Approaches