Publication: Weak Instruments in Growth Regressions: Implications for Recent Cross-Country Evidence on Inequality and Growth
Loading...
Published
2015-11
ISSN
Date
2015-12-18
Author(s)
Editor(s)
Abstract
This paper revisits four recent cross-country empirical studies on the effects of inequality on growth. All four studies report strongly significant negative effects, using the popular system generalized method of moments estimator that is frequently used in cross-country growth empirics. This paper shows that the internal instruments relied on by this estimator in these inequality-and-growth regressions are weak, and that weak instrument-consistent confidence sets for the effect of inequality on growth include a wide range of positive and negative values. This suggests that strong conclusions about the effect of inequality on growth— in either direction—cannot be drawn from these studies. This paper also systematically explores a wide range of alternative sets of internal instruments, and finds that problems of weak instruments are pervasive across these alternatives. More generally, the paper illustrates the importance of documenting instrument strength, basing inferences on procedures that are robust to weak instruments, and considering alternative instrument sets when using the system generalized method of moments estimator for cross-country growth empirics.
Link to Data Set
Citation
“Kraay, Aart. 2015. Weak Instruments in Growth Regressions: Implications for Recent Cross-Country Evidence on Inequality and Growth. Policy Research Working Paper;No. 7494. © World Bank. http://hdl.handle.net/10986/23456 License: CC BY 3.0 IGO.”
Digital Object Identifier
Associated URLs
Associated content
Other publications in this report series
Publication Climate and Social Sustainability in Fragility, Conflict, and Violence Contexts(Washington, DC: World Bank, 2026-01-07)Climate change is widely recognized as a driver of violent conflict, but its broader social effects remain less understood. Ignoring these dimensions risks a vicious cycle where climate policies might undermine socially just adaptation. Evidence is still limited on how climate shocks influence political participation, trust, or migration. This paper helps fill that gap by examining links between climate change, conflict, and social sustainability, with a focus on inclusion, resilience, cohesion, and legitimacy. Using secondary data from 2019–24, the study applies simple correlation-based methods to test three hypotheses on the nature, severity, and composition of these associations. The analysis combines multiple climate impact measures, new conflict classifications, recent social sustainability frameworks, and controls for population and geography. The results reveal strong correlations—not causation—between climate events and contexts of fragility, conflict, and violence. Climate impacts are most pronounced in both national and subnational conflict settings. The study also finds robust links between fragility, conflict, and violence and low levels of social sustainability, reflecting its role as both a driver and consequence of conflict. Some dimensions—such as violent events and insecurity—appear weaker in areas most affected by climate shocks. Two of the hypotheses are supported, and one remains inconclusive.Publication The Macroeconomic Implications of Climate Change Impacts and Adaptation Options(Washington, DC: World Bank, 2025-05-29)Estimating the macroeconomic implications of climate change impacts and adaptation options is a topic of intense research. This paper presents a framework in the World Bank's macrostructural model to assess climate-related damages. This approach has been used in many Country Climate and Development Reports, a World Bank diagnostic that identifies priorities to ensure continued development in spite of climate change and climate policy objectives. The methodology captures a set of impact channels through which climate change affects the economy by (1) connecting a set of biophysical models to the macroeconomic model and (2) exploring a set of development and climate scenarios. The paper summarizes the results for five countries, highlighting the sources and magnitudes of their vulnerability --- with estimated gross domestic product losses in 2050 exceeding 10 percent of gross domestic product in some countries and scenarios, although only a small set of impact channels is included. The paper also presents estimates of the macroeconomic gains from sector-level adaptation interventions, considering their upfront costs and avoided climate impacts and finding significant net gross domestic product gains from adaptation opportunities identified in the Country Climate and Development Reports. Finally, the paper discusses the limits of current modeling approaches, and their complementarity with empirical approaches based on historical data series. The integrated modeling approach proposed in this paper can inform policymakers as they make proactive decisions on climate change adaptation and resilience.Publication Institutional Capacity for Policy Implementation: An Analytical Framework(Washington, DC: World Bank, 2026-01-07)State capacity is an important prerequisite for policy implementation, yet at the country level it is difficult to measure, assess, and reform. This paper proposes a focus on institutional capacity: the ability of public institutions to implement the specific policy mandates for which they are responsible. Based on a review of existing literature, the paper defines the different dimensions that compose institutional capacity and groups them into two cross-cutting categories: organizational dimensions (personnel, financial resources, information systems, and management practices) and governance dimensions (transparency, independence, and accountability). The paper proposes measures for organizational and governance dimensions using existing data, shows intra-institutional variation of these measures within countries, and discusses how new data could be collected for better measurement of these concepts. Finally, the paper illustrates how the framework can be used to diagnose the sources of common problems related to weak policy implementation.Publication South Africa’s Fragmented Cities: The Unequal Burden of Labor Market Frictions(Washington, DC: World Bank, 2026-01-08)Using high-resolution administrative, census, and satellite data, this paper shows that South African cities are characterized by spatial mismatches between where people live and where jobs are located, relative to 20 global peers. Areas within 5 kilometers of commercial centers have 9,300 fewer residents per square kilometer than expected, which is 60 percent below the global median. Poor, dense neighborhoods are most affected. In Johannesburg, a 10-percentile increase in distance from the nearest business hub corresponds to a 3.7-percentile drop in asset wealth (a proxy of household wellbeing) and 4.9-percentile drop in employment. In Cape Town, the declines are 4.0 and 3.7 percentiles, respectively. Employment is 87 percent lower in the poorest decile than the richest in Johannesburg and 61 percent lower in Cape Town. These findings suggest that South Africa’s spatial organization of people and economic activity constrains agglomeration and reinforces inequality. This methodology provides a scalable and standardized data-driven framework to analyze spatial accessibility and agglomeration frictions in complex, data-constrained urban systems.Publication Investment in Emerging and Developing Economies(Washington, DC: World Bank, 2026-01-07)The world faces a pressing challenge to meet key development objectives amid slowing growth and rising macroeconomic and geopolitical risks. With the number of job seekers rising rapidly, infrastructure shortfalls continuing to be large, and climate costs mounting, the case for a significant investment push has never been stronger. Yet the capacity to respond in many emerging markets and developing economies has eroded. Since the global financial crisis, investment growth has slowed to about half its pace in the 2000s, with both public and private investment weakening. Foreign direct investment inflows—a critical source of capital, technology, and managerial know-how—have also fallen sharply and become increasingly concentrated, leaving low-income countries with only a marginal share. The risks of further retrenchment are significant, as trade tensions, policy uncertainty, and elevated debt levels continue to weigh on investment. Reigniting momentum will require ambitious domestic reforms to strengthen institutions, rebuild macro-fiscal stability, and deepen trade and investment integration—the foundations of a supportive business climate. At the same time, international cooperation is indispensable. A renewed commitment to a predictable system of cross-border trade and investment flows, combined with scaled-up financial support and sustained technical assistance, is essential to help emerging markets and developing economies—especially low-income countries and economies in fragile and conflict situations—bridge financing gaps and implement the domestic reforms needed to restore investment as an engine of growth, jobs, and development.
Journal
Journal Volume
Journal Issue
Collections
Related items
Showing items related by metadata.
Publication What is the Impact of International Remittances on Poverty and Inequality in Latin America?(World Bank, Washington, DC, 2007-06)Workers' remittances have become a major source of income for developing countries. However, little is still known about their impact on poverty and inequality. Using a large cross-country panel dataset, the authors find that remittances in Latin American and Caribbean (LAC) countries have increased growth and reduced inequality and poverty. These results are robust to the use of different instruments that attempt to correct for the potential endogeneity of remittances. Household survey-based estimates for 10 LAC countries confirm that remittances have negative albeit relatively small inequality and poverty-reducing effects, even after imputations for the potential home earnings of migrants.Publication Asset Distribution, Inequality, and Growth(World Bank, Washington, DC, 2000-06)With the recent resurgence of interest in equity, inequality, and growth, the possibility of a negative relationship between inequality and economic growth, has received renewed interest in the literature. Faced with the prospect that high levels of inequality may persist, and give rise to poverty traps, policymakers are paying more attention to the distributional implications of macroeconomic policies. Because high levels of inequality may hurt overall growth, policymakers are exploring measures to promote growth and equity at the same time. How the consequences of inequality are analyzed, along with the possible cures, depends partly on how inequality is measured. The authors use assets (land) rather than income - and a GMM estimator - to examine the robustness of the relationship between inequality and growth that has been observed in the cross-sectional literature, but has been drawn into question by recent studies using panel techniques. They find evidence that asset inequality - but not income inequality - has a relatively large negative impact on growth. They also find that a highly unequal distribution of assets reduces the effectiveness of educational interventions. This means that policymakers should be more concerned about households' access to assets, and to the opportunities associated with them, than about the distribution of income. Long-term growth might be improved by measures to prevent large jumps in asset inequality - possibly irreversible asset loss because of exogenous shocks - and by policies to facilitate asset accumulation by the poor.Publication Finance and Macroeconomic Volatility(World Bank, Washington, DC, 2000-11)Countries with more developed financial sectors, experience fewer fluctuations in real per capita output, consumption, and investment growth. But the manner in which the financial sector develops matters. The relative importance of banks in the financial system is important in explaining consumption, and investment volatility. The proportion of credit provided to the private sector, best explains volatility of consumption, and output. The authors generate their main results using fixed-effects estimates with panel data from seventy countries for the years 1956-98. Their general findings suggest that the risk management, and information processing provided by banks, maybe especially important in reducing consumption, and investment volatility. The simple availability of credit to the private sector, probably helps smooth consumption, and GDP.Publication Growth is Good for the Poor(World Bank, Washington, DC, 2001-04)When average income rises, the average incomes of the poorest fifth of society rise proportionately. This is a consequence of the strong empirical regularity that the share of income accruing to the bottom quintile does not vary systematically with average income. The authors document this empirical regularity in a sample of 92 countries spanning the past four decades and show that it holds across regions, periods, income levels, and growth rates. The authors next ask whether the factors that explain cross-country differences in the growth rates of average incomes have differential effects on the poorest fifth of society. They find that several determinants of growth--such as good rule of law, opennness to international trade, and developed financial markets--have little systematic effect on the share of income that accrues to the bottom quintile. Consequently, these factors benefit the poorest fifth of society as much as everyone else. Thee is some weak evidence that stabilization from high inflation and reductions in the overall size of government not only increase growth but also increase the income share of the poorest fifth in society. Finally, the authors examine several factors commonly thought to disproportionately benefit the poorest in society, but find little evidence of their effects. The absence of robust findings emphasizes that relatively little is known about the broad forces that account for the cross-country and intertemporal variation in the share of income accruing to the poorest fifth of society.Publication It's Not Factor Accumulation : Stylized Facts and Growth Models(Washington, DC: World Bank, 2001-05)The article documents five stylized facts of economic growth: (1) the 'residual' (total factor productivity, tfp) rather than factor accumulation accounts for most of the income and growth differences across countries; (2) income diverges over the long run; (3) factor accumulation is persistent while growth is not, and the growth path of countries exhibits remarkable variation; (4) economic activity is highly concentrated, with all factors of production flowing to the richest areas; and (5) national policies are closely associated with long-run economic growth rates. These facts do not support models with diminishing returns, constant returns to scale, some fixed factor of production, or an emphasis on factor accumulation. However, empirical work does not yet decisively distinguish among the different theoretical conceptions of tfp growth. Economists should devote more effort toward modeling and quantifying tfp.
Users also downloaded
Showing related downloaded files
Publication Global Economic Prospects, June 2023(Washington, DC: World Bank, 2023-06-06)Global growth is projected to slow significantly in the second half of this year, with weakness continuing in 2024. Inflation pressures persist, and tight monetary policy is expected to weigh substantially on activity. The possibility of more widespread bank turmoil and tighter monetary policy could result in even weaker global growth. Rising borrowing costs in advanced economies could lead to financial dislocations in the more vulnerable emerging market and developing economies (EMDEs). In low-income countries, in particular, fiscal positions are increasingly precarious. Comprehensive policy action is needed at the global and national levels to foster macroeconomic and financial stability. Among many EMDEs, and especially in low-income countries, bolstering fiscal sustainability will require generating higher revenues, making spending more efficient, and improving debt management practices. Continued international cooperation is also necessary to tackle climate change, support populations affected by crises and hunger, and provide debt relief where needed. In the longer term, reversing a projected decline in EMDE potential growth will require reforms to bolster physical and human capital and labor-supply growth.Publication Tradenet in Ghana: Best Practice of the Use of Information Technology(Washington, DC: World Bank, 2004)Ever since the 1996 Singapore WTO meeting, trade facilitation has attracted major attention in international trade discussions and negotiations as a powerful way, together with policies that reduce trade barriers, to help countries to better integrate into the world economy and thus enhance their growth prospects. Singapore was an early adopter of trade facilitation and developed Tradenet, an IT tool to speed up trade transactions and connect most members of the trading community into a single data network. This paper briefly describes the achievements of Singapore's TradeNet, how it came about and what lessons it contains for other countries. Then the genesis of a similar Tradenet initiative and the approach adopted in Ghana are discussed.Publication Growth in Syria(Taylor and Francis, 2021-07-05)This paper addresses three questions: (1) what would have been the growth and income trajectory of Syria in the absence of war; (2) given the war, what explains the reduction in economic growth; and (3) what potential growth scenarios for Syria there could be in the aftermath of war. Conflict impact estimates point to negative GDP growth of −12% on average over 2011–2018, with output contracting to about one-third of the 2010 level. In post-conflict simulation scenarios, the growth drivers are affected by the assumed levels of reconstruction assistance, repatriation of refugees, and productivity improvements associated with three political settlement outcomes: a baseline (Sochi-plus) moderate scenario, an optimistic (robust political settlement) scenario, and a pessimistic (de facto balance of power) scenario. Respectively for these scenarios, GDP per capita average growth in the next two decades is projected to be 6.1%, 8.2%, or 3.1%, assuming a final and stable resolution of the conflict.Publication Digital Africa(Washington, DC: World Bank, 2023-03-13)All African countries need better and more jobs for their growing populations. "Digital Africa: Technological Transformation for Jobs" shows that broader use of productivity-enhancing, digital technologies by enterprises and households is imperative to generate such jobs, including for lower-skilled people. At the same time, it can support not only countries’ short-term objective of postpandemic economic recovery but also their vision of economic transformation with more inclusive growth. These outcomes are not automatic, however. Mobile internet availability has increased throughout the continent in recent years, but Africa’s uptake gap is the highest in the world. Areas with at least 3G mobile internet service now cover 84 percent of Africa’s population, but only 22 percent uses such services. And the average African business lags in the use of smartphones and computers as well as more sophisticated digital technologies that catalyze further productivity gains. Two issues explain the usage gap: affordability of these new technologies and willingness to use them. For the 40 percent of Africans below the extreme poverty line, mobile data plans alone would cost one-third of their incomes—in addition to the price of access devices, apps, and electricity. Data plans for small- and medium-size businesses are also more expensive than in other regions. Moreover, shortcomings in the quality of internet services—and in the supply of attractive, skills-appropriate apps that promote entrepreneurship and raise earnings—dampen people’s willingness to use them. For those countries already using these technologies, the development payoffs are significant. New empirical studies for this report add to the rapidly growing evidence that mobile internet availability directly raises enterprise productivity, increases jobs, and reduces poverty throughout Africa. To realize these and other benefits more widely, Africa’s countries must implement complementary and mutually reinforcing policies to strengthen both consumers’ ability to pay and willingness to use digital technologies. These interventions must prioritize productive use to generate large numbers of inclusive jobs in a region poised to benefit from a massive, youthful workforce—one projected to become the world’s largest by the end of this century.Publication Global Rapid Post-Disaster Damage Estimation (GRADE) Report(Washington, DC: World Bank, 2024-08-05)This Global Rapid Post-Disaster Damage Estimation (GRADE) report provides a synopsis of the estimated direct economic damage in Saint Vincent and the Grenadines (SVG) due to the passage Hurricane Beryl. The report is based on a rapid and remote post disaster damage assessment that follows the established GRADE methodology. Hurricane Beryl passed over southern SVG on July 1, 2024. Wind speeds ranged from a Category 4 hurricane in the southern Grenadines, then lessening to the north with Tropical Storm force winds felt on the main island of Saint Vincent. The objective of this report is to provide an estimate of the direct economic damage to physical assets caused by Hurricane Beryl in Saint Vincent and the Grenadines (SVG) and to provide information on the spatial distribution of damages to support development of a roadmap for recovery and reconstruction.