Sir William Arthur Lewis (23 January 1915 – 15 June 1991) published in 1954 what was to be his most influential development
economics article,
Economic Development with Unlimited Supplies of Labour (Manchester School). In this publication, he introduced what came to be called the
dual sector model, or the
"Lewis model".
Lewis combined an analysis of the historical experience of developed countries with the central ideas of the classical economists to produce a broad picture of the development process. In his theory, a "capitalist" sector develops by taking labour from a non-capitalist backward "subsistence" sector.
The
"subsistence" sector was
defined by Lewis as "that part of the economy which is
not using reproducible capital". It can also be adjusted as the
indigenous traditional sector or the
"self employed sector". The
per head output is comparatively lower in this sector and this is because it is
not fructified with capital. The "Dual Sector Model" is a theory of development in which
surplus labor from traditional agricultural sector is transferred to the modern industrial sector whose growth over time
absorbs the surplus labour, promotes industrialization and
stimulates sustained development.
In the model, the
subsistence agricultural sector is typically characterized by
low wages, an
abundance of labour, and
low productivity through a
labour-intensive production process.
Lewis
defined the "capitalist" sector as "that part of the economy which
uses reproducible capital and
pays capitalists thereof". The use of capital is controlled by the
capitalists, who
hire the services of labour. It includes
manufacturing, plantations, mines etc. The capitalist sector may be
private or public.
In contrast to the "subsistence" sector, the
capitalist manufacturing sector is defined by
higher wage rates as compared to the subsistence sector,
higher marginal productivity, and a
demand for more workers. Also, the capitalist sector is assumed to use a
production process that is
capital intensive, so
investment and capital formation in the manufacturing sector are possible over time as
capitalists' profits are
reinvested in the capital stock.
Improvement in the marginal productivity of labour in the agricultural sector is assumed to be a low priority as the hypothetical developing nation's investment is going towards the physical capital stock in the manufacturing sector.
The subsistence sector is governed by informal institutions and social norms so that producers do not maximize profits and workers can be paid above their marginal product. At an early stage of development, the "unlimited" supply of labour from the subsistence economy means that the capitalist sector can expand for some time without the need to raise wages. This results in higher returns to capital, which are reinvested in capital accumulation. In turn, the increase in the capital stock leads the "capitalists" to expand employment by drawing further labour from the subsistence sector.
Assumptions- The model assumes that a developing economy has a surplus of unproductive labor in the agricultural sector.
- These workers are attracted to the growing manufacturing sector where higher wages are offered.
- It also assumes that the wages in the manufacturing sector are more or less fixed.
- Entrepreneurs in the manufacturing sector make profit because they charge a price above the fixed wage rate.
- The model assumes that these profits will be reinvested in the business in the form of fixed capital.
- An advanced manufacturing sector means an economy has moved from a traditional to an industrialized one.
Given the assumptions of the model (for example, that the profits are reinvested and that capital accumulation does not substitute for skilled labour in production), the process becomes self-sustaining and leads to modernization and economic development.
The primary relationship between the two sectors is that
when the capitalist sector expands, it extracts or draws labour from the subsistence sector. This causes the
output per head of labourers who move from the subsistence sector to the capitalist sector to
increase. Since Lewis in his model considers
overpopulated labour surplus economies he
assumes that the supply of unskilled labour to the capitalist sector is
unlimited. This gives rise to the
possibility of creating new industries and expanding existing ones at the existing wage rate. A large portion of the unlimited supply of labor consists of those who are in
disguised unemployment in agriculture and in other
over-manned occupations such as
domestic services, casual jobs, petty retail trading. Lewis also accounts for
two other factors that cause an
increase in the supply of unskilled labour, they are
women (confined to) the household and
population growth.
The
agricultural sector has a
limited amount of land to cultivate, the
marginal product of an additional farmer is
assumed to be
zero as the law of diminishing marginal returns has run its course due to the
fixed input of land. As a result, the
agricultural sector has a quantity of
farm workers who are not contributing to agricultural output since their
marginal productivities are zero. This group of farmers that is not producing any output is termed
surplus labour since this cohort could be moved to another sector with no effect on agricultural output. (The term surplus labour here is not being used in a
Marxist context and only refers to the
unproductive workers in the agricultural sector.) Therefore, due to the
wage differential between the capitalist and subsistence sector,
workers will tend to
transition from the agricultural to the manufacturing sector over time to reap the reward of
higher wages. However, even though the
marginal product of labor is zero, it still shares a part in the
total product and
receives approximately the average product.
Relationship between the two sectors = impact 0f shifting supply of labourers: If a quantity of workers moves from the subsistence to the capitalist sector equal to the quantity of
surplus labour in the subsistence sector, regardless of who actually transfers,
general welfare and productivity will improve (because
only surplus labour has shifted).
Total agricultural product will remain
unchanged while
total industrial product increases due to the addition of (surplus agricultural) labour, but the
additional labour also
drives down marginal productivity and wages in the manufacturing sector.
Over time as this transition continues to take place and investment results in increases in the capital stock, the
marginal productivity of workers in the
manufacturing will be
driven up by capital formation and
driven down by additional workers entering the manufacturing sector.
Eventually, the
wage rates of the agricultural and manufacturing sectors will equalize as (
no longer surplus) workers leave the agriculture sector for the manufacturing sector,
increasing marginal productivity and wages in agriculture whilst
driving down productivity and wages in manufacturing. The end result of this transition process is that the
agricultural wage equals the manufacturing wage, the
agricultural marginal product of labour equals the manufacturing marginal product of labour, and
no further manufacturing sector enlargement takes place as workers
no longer have a
monetary incentive to transition.
Surplus labour can be used instead of capital in the
creation of new industrial investment projects, or it can be
channeled into nascent industries, which are
labour-intensive in their early stages. Such growth
does not raise the value of the subsistence wage, because the
supply of labor exceeds the demand at that wage, and
rising production via improved labour techniques has the effect of
lowering the capital coefficient. Although labour is assumed to be in surplus, it is
mainly unskilled. This
inhibits growth since
technical progress necessary for growth requires skilled labor. But should there be a l
abor surplus and a modest capital, this bottleneck can be broken through the
provision of training and education facilities. The
utility of unlimited supplies of labour to growth objectives
depends upon the amount of capital available at the same time. Should there be surplus labour, agriculture will derive
no productive use from it, so a
transfer to a non-agriculture sector will be of
mutual benefit. It provides
jobs to the agrarian population and
reduces the burden of population from land.
Industry now obtains its labour. Labour must be
encouraged to move to increase productivity in agriculture. To start such a movement, the capitalist sector will have to pay a
compensatory payment determined by the wage rate that people can earn outside their present sector, plus a set of other amounts includes the
cost of living in the new sector and changes in the level of profits in the existing sector. The
margin capitalists may have to pay is
as much as 30 per cent above the average subsistence wage.
The
point at which the
excess labor in the subsistence sector is fully absorbed into the modern sector, and where
further capital accumulation begins to increase wages, is sometimes called the
Lewisian turning point. It has recently been widely discussed in the context of
economic development in China.
The Lewis turning point is a situation in
economic development where
surplus rural labor is fully absorbed into the manufacturing sector. This typically
causes agricultural and unskilled industrial real wages to rise. Shortly after the Lewis point, an
economy requires balanced growth policies.
Typically, reaching the
Lewis turning point causes an
increase in the wage bill and the
functional distribution favoring labor. However, in some cases such as in
Japan from 1870 to 1920,
agricultural labor productivity increased significantly and produced a
labor surplus,
dampening the rise in real wages.
According to a study by Zhang and Yang,
China reached the Lewis point in 2010;
cheap labor in the country
has rapidly decreased and
real agricultural wages have substantially increased. Despite its large population,
in the early 2010s China faced labor shortages, and
real wages nearly doubled since 2003. Such
rapid rise in wages for unskilled work is a
key indicator of reaching the Lewis point. However, other journals such as the
China Economic Review claim that China has
not reached the Lewis point, comparing the effect of the Lewis point in China to the Japanese experience. A
2013 working paper by the
International Monetary Fund predicts the Lewis point in China to "emerge between 2020 and 2025".
In their 2017 book
Artificial Intelligence and Economic Theory: Skynet in the Market,
Tshilidzi Marwala and
Evan Hurwitz used Arthur Lewis theory to understand the transition of the economy into the
Fourth Industrial Revolution where
much of the production in the economy is automated by artificially intelligent machines. In this regard, they identified an
equilibrium point, i.e.
Lewis turning point, where
automating human labor does not result in additional economic benefit.
Dual-Sector Model (developing economies) ..