Development Economics: Theories, Indicators, Poverty and Growth Models
2. Schumpeter, Rostow's stages, and the balanced-growth debate
Joseph Schumpeter makes the entrepreneur the engine of development through innovation — new goods, new methods, new markets, new sources of supply, new forms of organisation — financed by bank credit. Innovation arrives in clusters and sweeps away old firms in a process he called creative destruction; this drives the business cycle. He sharply separates invention (a new idea) from innovation (its first commercial use). W. W. Rostow describes five stages of growth: traditional society, the preconditions for take-off, the take-off (a sharp rise in the investment rate and a few leading sectors), the drive to maturity, and the age of high mass consumption.
The post-war debate on strategy pits balanced against unbalanced growth. Nurkse and Rosenstein-Rodan argue for balanced growth: a poor country is trapped in a vicious circle of low income, low saving and a small market, so a wide, simultaneous wave of investment across many industries is needed, each creating demand for the others. Rosenstein-Rodan's Big Push stresses indivisibilities (in social overhead capital, in demand, and in saving) that make a minimum critical effort necessary. Hirschman replies with unbalanced growth: deliberately create imbalances by investing in sectors with strong linkages (backward to suppliers, forward to users); the resulting shortages and pressures induce further investment, economising on scarce decision-making ability.
3. Indicators of development: HDI, MDGs and SDGs
Per-capita income measures the size of the pie but not health, education or distribution, so development is tracked by broader indicators. The Human Development Index (HDI), from the UNDP's Human Development Reports, combines three dimensions: a long and healthy life (life expectancy), knowledge (expected and mean years of schooling) and a decent standard of living (GNI per capita at PPP, entered in logs). Each is converted to an index between 0 and 1 by (actual − minimum)/(maximum − minimum), and the three are combined as a geometric mean, which penalises uneven achievement across dimensions more than a simple average would.
Goal frameworks set the global agenda. The Millennium Development Goals (MDGs) ran as eight goals for the period up to 2015 and focused on extreme poverty, primary education, gender, child and maternal health, disease and environmental sustainability. They were succeeded by the Sustainable Development Goals (SDGs), seventeen goals to be reached by 2030, which are broader (they include inequality, decent work, sustainable cities and climate action), apply to all countries rather than only developing ones, and are universal and integrated rather than a short checklist.
4. Poverty and inequality: concepts and measurement
Poverty is measured against a poverty line (a minimum consumption or income). The simplest measure is the headcount ratio, the fraction of people below the line. Its weakness is that it ignores depth: it does not change if a poor person falls further below the line. The poverty gap index fixes this by averaging each poor person's shortfall from the line (as a fraction of the line) over the whole population, and the squared poverty gap goes further by weighting larger shortfalls more, so it captures severity. These three belong to the Foster-Greer-Thorbecke (FGT) family. The Sen index combines the headcount, the poverty gap and inequality among the poor into one number.
Inequality is read from the Lorenz curve, which plots the cumulative share of income against the cumulative share of population, ranked from poorest to richest; the 45-degree line is perfect equality, and the further the curve bows below it, the greater the inequality. The Gini coefficient is the area between the equality line and the Lorenz curve divided by the whole area under the equality line, so it runs from 0 (perfect equality) to 1 (perfect inequality). The Kuznets hypothesis adds a dynamic claim: inequality first rises and then falls as an economy develops, tracing an inverted U.
6. Models of economic growth: Harrod-Domar, Solow, Ramsey and endogenous growth
The Harrod-Domar model makes growth depend on capital alone. With a fixed capital-output ratio v (no substitution between capital and labour) and a saving rate s, the warranted rate of growth is g = s/v: save more, or use capital more productively (lower v), and the economy grows faster. Its famous difficulty is the knife-edge: the warranted rate need not equal the natural rate (labour-force growth plus technical progress), and any gap widens rather than self-corrects, so steady growth is a fluke. It remains the workhorse behind development planning, where s/ICOR gives a required investment rate for a target growth rate.
The Solow model restores substitution and diminishing returns to capital. Per worker, capital accumulates as savings add to it and depreciation and population growth dilute it, so the economy converges to a steady state where s·f(k) = (n + δ)k; beyond it, extra capital earns too little to maintain itself. The sharp conclusion is that in the long run per-capita growth requires technical progress, which the basic model leaves exogenous. The Ramsey (Ramsey-Cass-Koopmans) model closes this gap on the saving side by letting optimising households choose saving to maximise lifetime utility, so the saving rate is derived rather than assumed.
Technical progress comes in two forms. Disembodied progress raises the productivity of all capital at once, old and new alike, as a general shift in the production function. Embodied progress is carried only by new vintages of capital, so it is realised only through fresh investment that replaces old equipment. Endogenous growth theory makes the growth rate come from within the model rather than from an exogenous residual: by treating knowledge and human capital as inputs with increasing returns or spillovers (Romer, Lucas), or in the simplest AK form by assuming capital broadly defined does not suffer diminishing returns, saving and investment can sustain growth indefinitely without an exogenous push.
Key takeaways
- Smith sees self-sustaining growth from the division of labour and accumulation, limited by the market's size; Ricardo sees diminishing returns on fixed land dragging the economy to a stationary state; Marx sees surplus value and accumulation producing class conflict and crisis.
- Schumpeter's entrepreneur drives development by innovation and creative destruction; Rostow lays out five stages with take-off at the centre. Balanced growth (Nurkse, Rosenstein-Rodan's Big Push) invests widely and at once; Hirschman's unbalanced growth invests in high-linkage sectors to induce the rest.
- The HDI combines health, education and income as a geometric mean of three normalised indices. The MDGs were eight goals to 2015; the SDGs are seventeen goals to 2030, broader and universal.
- The headcount ratio ignores depth; the poverty gap and squared poverty gap (the FGT family) and the Sen index capture depth and severity. Inequality is read from the Lorenz curve, and the Gini coefficient runs from 0 (equality) to 1 (inequality).
- The demographic transition shifts age structure; a low dependency ratio opens a demographic dividend that pays off only with jobs, education and health. Social development is tracked by mortality, morbidity, fertility, gender gaps, migration and child labour.
- Harrod-Domar gives g = s/v with a knife-edge instability; Solow adds diminishing returns and converges to a steady state where s·f(k) = (n + δ)k, so long-run per-capita growth needs technical progress. Ramsey derives saving from optimisation, and endogenous growth makes the growth rate internal through knowledge and human capital.
Practice questions (17)
Attempt each one before opening the answer. Every explanation names the tempting wrong option as well as the right one, because that is where marks are lost.
In David Ricardo's account of development, the economy tends over time toward a stationary state mainly because:
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Answer: C — Fixed land and diminishing returns raise rent and squeeze profits toward zero
Ricardo's engine of pessimism is diminishing returns on a fixed supply of land: as cultivation extends to poorer land, rent rises and profits are squeezed toward zero, halting accumulation. The innovation-exhaustion idea belongs to a Schumpeterian frame, not Ricardo, and the monetary and permanently-rising-wage stories are not his mechanism.Schumpeter's phrase "creative destruction" refers to:
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Answer: B — The way innovation by entrepreneurs sweeps away established firms and products
Creative destruction is Schumpeter's name for the process in which entrepreneurial innovation continually displaces incumbent firms, methods and products, driving growth and the business cycle. The collapse-through-crisis idea is Marxian, and the deliberate-imbalance idea is Hirschman's unbalanced growth, both close but distinct from Schumpeter's mechanism.A planner argues that a poor country should invest simultaneously across many industries at once, because each new industry creates the demand that makes the others profitable. This argument is closest to:
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Answer: D — The balanced-growth doctrine of Nurkse and the Big Push of Rosenstein-Rodan
Investing widely and simultaneously so that industries create demand for each other is the balanced-growth argument of Nurkse, and the coordinated minimum effort it needs is Rosenstein-Rodan's Big Push. Hirschman argues the opposite, that deliberate imbalance in high-linkage sectors is better, while Rostow and Solow describe stages and convergence rather than an investment strategy.Rosenstein-Rodan's Big Push rests on the idea of indivisibilities. Which of these best explains why they make a single large coordinated investment necessary?
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Answer: A — Lumpy social overhead capital and demand complementarities make small, isolated investments unprofitable on their own
The Big Push argues that infrastructure comes in large lumps and that each industry's output is another's demand, so a scattering of small investments fails while a coordinated large one succeeds. Diminishing returns and a fixed capital-output ratio belong to Solow and Harrod-Domar, and perfect information would remove the coordination problem the Big Push is designed to solve.Which of the following correctly match a thinker with a central idea in development theory?
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Answer: A — Adam Smith: the division of labour is limited by the extent of the market; B — Karl Marx: profit originates in the surplus value created by labour beyond its wage; C — W. W. Rostow: development proceeds through five stages with a take-off at its core
Smith's market-extent limit, Marx's surplus value as the source of profit, and Rostow's five stages with the take-off are all correctly paired. The last pairing is wrong: innovation and creative destruction are Schumpeter's, not Ricardo's, whose signature idea is diminishing returns leading to a stationary state.The Human Development Index combines three dimensions. Which set correctly lists them?
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Answer: B — A long and healthy life, knowledge, and a decent standard of living
The HDI's three dimensions are a long and healthy life (life expectancy), knowledge (schooling) and a decent standard of living (GNI per capita). The tempting wrong set pairs life expectancy with poverty and inequality measures, which belong to separate indices; the HDI does not include the headcount ratio or the Gini coefficient as components.Which of the following statements about the HDI, the MDGs and the SDGs are correct?
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Answer: A — Since 2010 the HDI is computed as the geometric mean of its three dimension indices; B — The Millennium Development Goals were a set of eight goals with a target year of 2015; C — The Sustainable Development Goals are seventeen goals to be achieved by 2030
The HDI is a geometric mean since 2010, the MDGs were eight goals to 2015, and the SDGs are seventeen goals to 2030, all standard facts. The last claim is false: because the HDI weights health and education alongside income, a rise in income alone changes only one of the three indices and does not raise the HDI automatically.A country's HDI dimension indices are: health index 0.9, education index 0.6, and income index 0.4. Using the current UNDP method (the geometric mean of the three indices), the Human Development Index is ____ (give two decimal places).
Numerical answer — type the value.
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Answer: 0.60
The geometric mean is the cube root of the product: (0.9 x 0.6 x 0.4) = 0.216, and the cube root of 0.216 is 0.60. Taking the arithmetic mean instead would give (0.9 + 0.6 + 0.4)/3 = 0.63, which is the common mistake; the geometric mean is lower because it penalises the uneven achievement across the three dimensions.A government scheme lifts several households that were just below the poverty line to just above it, while the very poorest households are left unchanged. Which measure is most likely to show an improvement that overstates the gain to the poor?
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Answer: B — The headcount ratio, because it only counts how many people are below the line
The headcount ratio counts only how many are below the line, so moving people from just below to just above makes it fall sharply while telling us nothing about the untouched poorest, overstating the gain. The poverty gap and squared poverty gap would register the unchanged deepest poverty, which is exactly why they are preferred as depth-sensitive measures.In an economy the poorer half of the population receives 20% of total income and the richer half receives the remaining 80%. Treating each half as a single point on the Lorenz curve, the Gini coefficient is ____ (give two decimal places).
Numerical answer — type the value.
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Answer: 0.30
The Lorenz curve passes through (0, 0), (0.5, 0.2) and (1, 1). The area under it is the first triangle, 0.5 x 0.2 / 2 = 0.05, plus the trapezoid from 0.5 to 1, (0.2 + 1.0)/2 x 0.5 = 0.30, giving 0.35. The Gini is (0.5 - 0.35)/0.5 = 0.30. Forgetting to divide the area between the curves by 0.5 gives 0.15, the usual slip.Which of the following statements about the measurement of poverty and inequality are correct?
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Answer: A — The Gini coefficient takes the value 0 under perfect equality and approaches 1 as inequality increases; B — The headcount ratio is insensitive to how far below the poverty line the poor actually are; C — The Lorenz curve coincides with the 45-degree line when income is perfectly equally distributed
The Gini runs from 0 to 1, the headcount ratio ignores the depth of poverty, and a perfectly equal distribution gives a Lorenz curve on the 45-degree line, all standard. The Gini cannot exceed 1 for an ordinary income distribution, so the claim about a value above 1 is false; such a value would be a computational error rather than a feature of the economy.A country's demographic dividend refers to:
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Answer: C — The growth potential from a large working-age share and a low dependency ratio
The demographic dividend is the growth potential that opens when the working-age share is large and the dependency ratio low, during the demographic transition. A higher fertility rate would raise dependency, not lower it, and the dividend is a potential that requires jobs, education and health to be realised, not an automatic or guaranteed gain.Which of the following statements about social-sector development and demography are correct?
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Answer: A — Morbidity refers to the presence of disease, while mortality refers to death rates; B — In the demographic transition, death rates typically begin to fall before birth rates do; C — A falling total fertility rate is usually associated with rising female education and child survival
Morbidity is about illness and mortality about death, death rates fall before birth rates in the transition, and lower fertility tracks higher female education and child survival, all standard. The claim about a high dependency ratio reverses the definition: a high dependency ratio means dependents are large relative to the working-age population, not the other way round.In the basic Solow growth model, long-run growth in output per worker ultimately depends on:
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Answer: B — The rate of exogenous technical progress
Because capital runs into diminishing returns, saving more only raises the level of income per worker, not its long-run growth rate; sustained per-capita growth in the basic Solow model comes only from exogenous technical progress. A higher saving rate gives a one-time level effect, and population growth and depreciation set where the steady state lies, not the long-run growth rate.In the Harrod-Domar model, the saving rate is 24% of income and the capital-output ratio is 4. The warranted rate of growth (g = s/v), expressed in percent, is ____.
Numerical answer — type the value.
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Answer: 6
The warranted rate is the saving rate divided by the capital-output ratio: g = s/v = 0.24 / 4 = 0.06, that is 6%. Multiplying instead of dividing, or using 24 x 4, gives nonsensical figures; the ratio v is the extra capital needed per extra unit of output, so a higher v lowers growth for a given saving rate.In a Solow economy, output per worker is y = k^0.5, where k is capital per worker. The saving rate is 0.4, the depreciation rate is 0.1, and there is neither population growth nor technical progress. The steady-state capital per worker k* is ____.
Numerical answer — type the value.
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Answer: 16
At the steady state, saving per worker equals the capital needed to cover depreciation and population growth: s x k^0.5 = (n + delta) x k, so 0.4 k^0.5 = 0.1 k. Dividing by k^0.5 gives 0.4 = 0.1 k^0.5, so k^0.5 = 4 and k* = 16. A common slip is to stop at k^0.5 = 4 and report 4, which is the steady-state output per worker y, not k.Which one of the following statements about technical progress and growth theory is correct?
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Answer: A — Embodied technical progress is carried only by new capital, so it is realised through fresh investment
Embodied progress is built into new vintages of capital and so needs investment to be realised, while disembodied progress raises the productivity of all capital at once. Endogenous growth theory does the opposite of the other options: it relaxes sharply diminishing returns (through knowledge and human capital with spillovers) so that the growth rate is determined inside the model, not outside it.
5. Social-sector development and the demographic dividend
Development is social as well as economic. Health is tracked by mortality (infant, child and maternal mortality rates) and morbidity (the prevalence and incidence of disease); education by enrolment, literacy and years of schooling; gender by gaps in these outcomes and in work and pay. Fertility (the total fertility rate, births per woman) tends to fall as income, female education and child survival rise. Migration reallocates labour from low- to high-productivity locations, and child labour both reflects poverty and perpetuates it by cutting short schooling.
The demographic transition moves a population from high birth and death rates to low ones in stages: death rates fall first (better health and nutrition), birth rates fall later, and in between the population grows fast and its age structure shifts. When the working-age share is large and the dependency ratio (young plus old, divided by working-age) is low, the economy enjoys a demographic dividend: more workers, more saving and potentially faster growth. The dividend is a window, not a guarantee: it pays off only if the extra workers find productive jobs and adequate education and health, and it eventually closes as the population ages.