Within-Country Inequality and the Shaping of a Just Global Climate Policy
Marie Young-Brun, Francis Dennig, Frank Errickson, Stéphane Zuber
Proceedings of the National Academy of Sciences of the United States of America (PNAS),
Nr. 39,
2025
Abstract
Climate policy design must balance emissions mitigation with concerns for fairness, particularly as climate change disproportionately affects the poorest households within and across countries. Integrated Assessment Models used for global climate policy evaluation have so far typically not considered inequality effects within countries. To fill this gap, we develop a global Integrated Assessment Model representing national economies and subnational income, mitigation cost, and climate damage distribution and assess a range of climate policy schemes with varying levels of effort sharing across countries and households. The schemes are consistent with limiting temperature increases to 2 °C and account for the possibility to use carbon tax revenues to address distributional effects within and between countries. We find that carbon taxation with redistribution improves global welfare and reduces inequality, with the most substantial gains achieved under uniform taxation paired with global per capita transfers. A Loss and Damage mechanism offers significant welfare improvements in vulnerable countries while requiring only a modest share of global carbon revenues in the medium term. The poorest households within all countries may benefit from the transfer scheme, in particular when some redistribution is made at the country level. Our findings underscore the potential for climate policy to advance both environmental and social goals, provided revenue recycling mechanisms are effectively implemented. In particular, they demonstrate the feasibility of a welfare improving global climate policy involving limited international redistribution.
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Assumption Errors and Forecast Accuracy: A Partial Linear Instrumental Variable and Double Machine Learning Approach
Katja Heinisch, Fabio Scaramella, Christoph Schult
IWH Discussion Papers,
Nr. 6,
2025
Abstract
Accurate macroeconomic forecasts are essential for effective policy decisions, yet their precision depends on the accuracy of the underlying assumptions. This paper examines the extent to which assumption errors affect forecast accuracy, introducing the average squared assumption error (ASAE) as a valid instrument to address endogeneity. Using double/debiased machine learning (DML) techniques and partial linear instrumental variable (PLIV) models, we analyze GDP growth forecasts for Germany, conditioning on key exogenous variables such as oil price, exchange rate, and world trade. We find that traditional ordinary least squares (OLS) techniques systematically underestimate the influence of assumption errors, particularly with respect to world trade, while DML effectively mitigates endogeneity, reduces multicollinearity, and captures nonlinearities in the data. However, the effect of oil price assumption errors on GDP forecast errors remains ambiguous. These results underscore the importance of advanced econometric tools to improve the evaluation of macroeconomic forecasts.
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Step by Step ‒ A Quarterly Evaluation of EU Commission's GDP Forecasts
Katja Heinisch
Journal of Forecasting,
Nr. 3,
2025
Abstract
The European Commission’s growth forecasts play a crucial role in shaping policies and provide a benchmark for many (national) forecasters. The annual forecasts are built on quarterly estimates, which do not receive much attention and are hardly known. Therefore, this paper provides a comprehensive analysis of multi-period ahead quarterly GDP growth forecasts for the European Union (EU), euro area, and several EU member states with respect to first-release and current-release data. Forecast revisions and forecast errors are analyzed, and the results show that the forecasts are not systematically biased. However, GDP forecasts for several member states tend to be overestimated at short-time horizons. Furthermore, the final forecast revision in the current quarter is generally downward biased for almost all countries. Overall, the differences in mean forecast errors are minor when using real-time data or pseudo-real-time data and these differences do not significantly impact the overall assessment of the forecasts’ quality. Additionally, the forecast performance varies across countries, with smaller countries and Central and Eastern European countries (CEECs) experiencing larger forecast errors. The paper provides evidence that there is still potential for improvement in forecasting techniques both for nowcasts but also forecasts up to eight quarters ahead. In the latter case, the performance of the mean forecast tends to be superior for many countries.
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Alumni
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Lehre
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Scientific Quality In order to secure the highest standards, the courses and the research projects will be evaluated. Evaluations form the basis for further improvements in…
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Conference on innovation and productivity in the aftermath of the pandemic
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„Evaluation der Gemeinschaftsaufgabe ‚Verbesserung der regionalen Wirtschaftsstruktur‘ (GRW)“ durch einzelbetriebliche Erfolgskontrolle – Evaluationsbericht –
Matthias Brachert, Eva Dettmann, Lutz Schneider, Mirko Titze
IWH Studies,
Nr. 3,
2024
Abstract
Gegenstand dieses Evaluationsberichts ist die Replikation und Erweiterung der Ergebnisse des vorhergehenden Gutachtens zur Evaluation der Gemeinschaftsaufgabe ‚Verbesserung der regionalen Wirtschaftsstruktur‘ (GRW)
Der vorliegende Evaluationsbericht verfolgt zwei Ziele. Erstens aktualisiert er die Ergebnisse aus dem vorherigen Gutachten. Zweitens betrachtet er einige Aspekte zu den Wirkungen der GRW-Förderung vertiefend. Dazu gehört insbesondere die Frage, ob die GRW für die geförderten Betriebe tatsächlich einen Anreizeffekt im Sinne einer Ausweitung der Investitionstätigkeit hatte und wie sich die Effekte der Förderung unter Verwendung fortgeschrittener Produktivitätsmaße darstellt. Des Weiteren widmet sich der Evaluationsbericht einer vertiefenden Untersuchung heterogener Effekte auf sektoral disaggregierter Ebene sowie nach Betriebsgrößenklassen. Wo es möglich ist, analysiert der Bericht zudem längere Zeiträume nach dem Beginn des Förderprojekts. Schließlich widmet sich der Evaluationsbericht Fragen zur Wirtschaftlichkeit des GRW-Programms auf einzelbetrieblicher Ebene, indem er die Effekte in Beziehung setzt zur Höhe der aufgewendeten Fördermittel.
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