This issue of the IMF Research Bulletin features recommended readings from IMF Publications and an update on recent IMF Working Papers and IMF Staff Discussion Notes. It also includes a special announcement welcoming Linda Tesar (University of Michigan) as the new editor of “IMF Economic Review.” The Q&A section explores “Seven Questions on China-Africa Relations” (Luiz Almeida, Wenjie Chen, and Oral Williams). The Research Summaries surveys “Income Polarization in the United States” (Ali Alichi, Kory Kantenga, and Juan Sole); and “The Future Wealth of Nations: World Trade in Services” (Prakash Loungani, Saurabh Mishra, Chris Papageorgiou, and Ke Wang).

The paper uses a combination of micro-level datasets to document the rise of income polarization—what some have referred to as the “hollowing out” of the income distribution—in the United States, since the 1970s. While in the initial decades more middle-income households moved up, rather than down, the income ladder, since the turn of the current century, most of polarization has been towards lower incomes. This result is striking and in contrast with findings of other recent contributions. In addition, the paper finds evidence that, after conditioning on income and household characteristics, the marginal propensity to consume from permanent changes in income has somewhat fallen in recent years. We assess the potential impacts of these trends on private consumption. During 1998-2013, the rise in income polarization and lower marginal propensity to consume have suppressed the level of real consumption at the aggregate level, by about 31⁄2 percent—equivalent to more than one year of consumption.

The Fall 2017 IMF Research Bulletin includes a Q&A article covering "Seven Questions on the Globalization of Farmland" by Christian Bogmans. The first research summary, by Manmohan Singh and Haobing Wang is "Central Bank Balance Sheet Policies: Some Policy Implications." The second research summary is "Leaning Against the Windy Bank Lending" by Giovanni Melina and Stefania Villa. A listing of new IMF Working Papers and Staff Discussion Notes is featured, as well as new titles from IMF Publications. Information on IMF Economic Review is also included.

Using a newly constructed dataset on trade in services for 192 countries from 1970 to 2014, this paper shows that services currently constitute one-fourth of world trade and an increasingly important component of global production. A detailed analysis of patterns and stylized facts reveals that exports of services are not only gaining strong momentum and catching up with exports of goods in many countries, but they could also trigger a new wave of trade globalization. Research applications of the trade in service dataset on structural transformation, resilience, labor reallocation, and income distribution are outlined.

The Summer 2017 issue of the IMF Research Bulletin highlights new research such as recent IMF Working Papers and Staff Discussion Notes. The Research Summaries are “Structural Reform Packages, Sequencing, and the Informal Economy (by Zsuzsa Munkacsi and Magnus Saxegaard) and “A Broken Social Contract, Not High Inequality Led to the Arab Spring” (by Shantayanan Devarajan and Elena Ianchovichina). The Q&A section features “Seven Questions on Fintech” (by Tommaso Mancini-Griffoli). The Bulletin also includes information on recommended titles from IMF Publications and the latest articles from the IMF Economic Review.

“Leaning against the wind” (LAW) with a higher monetary policy interest rate may have benefits in terms of lower real debt growth and associated lower probability of a financial crisis but has costs in terms of higher unemployment and lower inflation, importantly including a higher cost of a crisis when the economy is weaker. For existing empirical estimates, costs exceed benefits by a substantial margin, even if monetary policy is nonneutral and permanently affects real debt. Somewhat surprisingly, less effective macroprudential policy and generally a credit boom, with resulting higher probability, severity, or duration of a crisis, increases costs of LAW more than benefits, thus further strengthening the strong case against LAW.

Is there a minimum tax to GDP ratio associated with a significant acceleration in the process of growth and development? We give an empirical answer to this question by investigating the existence of a tipping point in tax-to-GDP levels. We use two separate databases: a novel contemporary database covering 139 countries from 1965 to 2011 and a historical database for 30 advanced economies from 1800 to 1980. We find that the answer to the question is yes. Estimated tipping points are similar at about 123⁄4 percent of GDP. For the contemporary dataset we find that a country just above the threshold will have GDP per capita 7.5 percent larger, after 10 years. The effect is tightly estimated and economically large.

Introduction.Big data for twenty-first-century economic statistics: the future is now /Katharine G. Abraham, Ron S. Jarmin, Brian C. Moyer, and Matthew D. Shapiro --Toward comprehensive use of big data in economic statistics.Reengineering key national economic indicators /Gabriel Ehrlich, John Haltiwanger, Ron S. Jarmin, David Johnson, and Matthew D. Shapiro ;Big data in the US consumer price index: experiences and plans /Crystal G. Konny, Brendan K. Williams, and David M. Friedman ;Improving retail trade data products using alternative data sources /Rebecca J. Hutchinson ;From transaction data to economic statistics: constructing real-time, high-frequency, geographic measures of consumer spending /Aditya Aladangady, Shifrah Aron-Dine, Wendy Dunn, Laura Feiveson, Paul Lengermann, and Claudia Sahm ;Improving the accuracy of economic measurement with multiple data sources: the case of payroll employment data /Tomaz Cajner, Leland D. Crane, Ryan A. Decker, Adrian Hamins-Puertolas, and Christopher Kurz --Uses of big data for classification.Transforming naturally occurring text data into economic statistics: the case of online job vacancy postings /Arthur Turrell, Bradley Speigner, Jyldyz Djumalieva, David Copple, and James Thurgood ;Automating response evaluation for franchising questions on the 2017 economic census /Joseph Staudt, Yifang Wei, Lisa Singh, Shawn Klimek, J. Bradford Jensen, and Andrew Baer ;Using public data to generate industrial classification codes /John Cuffe, Sudip Bhattacharjee, Ugochukwu Etudo, Justin C. Smith, Nevada Basdeo, Nathaniel Burbank, and Shawn R. Roberts --Uses of big data for sectoral measurement.Nowcasting the local economy: using Yelp data to measure economic activity /Edward L. Glaeser, Hyunjin Kim, and Michael Luca ;Unit values for import and export price indexes: a proof of concept /Don A. Fast and Susan E. Fleck ;Quantifying productivity growth in the delivery of important episodes of care within the Medicare program using insurance claims and administrative data /John A. Romley, Abe Dunn, Dana Goldman, and Neeraj Sood ;Valuing housing services in the era of big data: a user cost approach leveraging Zillow microdata /Marina Gindelsky, Jeremy G. Moulton, and Scott A. Wentland --Methodological challenges and advances.Off to the races: a comparison of machine learning and alternative data for predicting economic indicators /Jeffrey C. Chen, Abe Dunn, Kyle Hood, Alexander Driessen, and Andrea Batch ;A machine learning analysis of seasonal and cyclical sales in weekly scanner data /Rishab Guha and Serena Ng ;Estimating the benefits of new products /W. Erwin Diewert and Robert C. Feenstra.

The multiple indicator-multiple cause (MIMIC) method is a well-established tool for measuring informal economic activity. However, it has been criticized because GDP is used both as a cause and indicator variable. To address this issue, this paper applies for the first time the light intensity approach (instead of GDP). It also uses the Predictive Mean Matching (PMM) method to estimate the size of the informal economy for Sub-Saharan African countries over 24 years. Results suggest that informal economy in Sub-Saharan Africa remains among the largest in the world, although this share has been very gradually declining. It also finds significant heterogeneity, with informality ranging from a low of 20 to 25 percent in Mauritius, South Africa and Namibia to a high of 50 to 65 percent in Benin, Tanzania and Nigeria.

The Research Summaries in this issue of the IMF Research Bulletin cover “Tax Capacity and Growth” (by Vitor Gaspar, Laura Jaramillo, and Philippe Wingender), and “U.S. Shale Revolution and Its Spillover Effects on the Global Economy” (Ravi Balakrishnan, Keiko Honjo, Akito Matsumoto, and Andrea Pescatori). The Q&A coauthored by Amadou Sy and Mariama Sow covers “Seven Questions about the Relationship between Country Finance and Governance.” A listing of recent IMF Working Papers, Staff Discussion Notes, and Recommended Readings from IMF Publications is included in the IMF Research Bulletin. Readers can also find news on free-to-view articles from IMF Economic Review and a call for conference papers in this issue of the Bulletin.