The Research Summaries in the March 2013 Research Bulletin discuss "Trade Finance and Its Role in the Great Trade Collapse" (JaeBin Ahn) and "Sovereign Debt: How to Track Who Is Buying and Selling It" (Serkan Arslanalp and Takahiro Tsuda). The Q&A looks at "Seven Questions on the Implications of Global Supply Chains for Real Effective Exchange Rates" (Rudolfs Bems). Readers can also find in this issue a listing of recent IMF Working Papers, Staff Discussion Notes, and Recommended Readings from IMF Publications. The Bulletin also includes a call for papers for a research conference and information on free access to the IMF Economic Review in April.

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 Research Summaries in the September 2013 IMF Research Bulletin focus on “External Conditions and Debt Sustainability in Latin America” (Gustavo Adler and Sebastian Sosa) and “Monetary Policy Cyclicality in Emerging Markets” (Donal McGettigan, Kenji Moriyama, and Chad Steinberg). In the Q&A, Itai Aigur and Sunil Sharma discuss “Seven Questions on Macroprudential Policy Frameworks.” The Research Bulletin also includes an updated listing of recent IMF Working Papers, Staff Discussion Notes, and Recommended Readings from the IMF Bookstore, as well as information on a forthcoming conference. The IMF Economic Review’s new Impact Factor is also highlighted.

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.

The Research Summaries in the March 2014 Research Bulletin focus on efficiency of health expenditure (Francesco Grigoli and Javier Kapsoli) and employment growth in European Union countries (Bas B. Bakker and Li Zeng). The Q&A article looks at “Seven Questions on Financial Interconnectedness” (Co-Pierre Georg and Camelia Minoiu). The Research Bulletin also includes a listing of IMF Working Papers, Staff Discussion Notes, and Recommended Readings from the IMF Bookstore. Information on the IMF Economic Review—the research journal of the IMF—is also provided.

This issue of the IMF Research Bulletin opens with a letter from the new editor, Rabah Arezki. The Research Summaries are a "Primer on 'Global Liquidity'" (Eugenio Cerutti, Stijn Claessens, and Lev Ratnovski); and "Trade Integration adn Business Cycle Synchronization" (Kevin Cheng, Romain Duval, and Dulani Senevirante). The Q&A column looks at "Seven Questions on the Global Housing Markets" (Hites Ahir, Heedon Kang, and Prakash Loungani). September 2014 issue of the Bulletin also includes updates on IMF Working Papers, Staff Discussion Notes, and Recommended Readings from the IMF Bookstore, as well as special announcements on new staff publications and the Fifteenth Annual Jacques Polak Research Conference. Also included is information on the latest issue of “IMF Economic Review” with a link to an article by Paul Krugman.

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.