I analyze market-order execution quality using order-based data reported in accordance with Securities and Exchange Commission Rule 11Ac1-5. These data facilitate a comprehensive investigation of multiple dimensions of execution quality, including measures of costs and speed, for large samples of common stocks on Nasdaq and the NYSE. The evidence is consistent with competitive equity markets. Overall execution costs on Nasdaq exceed those on the NYSE, but orders execute faster. This relationship reverses for larger orders exceeding 1,999 shares. The apparent trade-off between costs and speed suggests that inferring execution quality from costs alone could be problematical. It also illustrates the need for models of trader behavior that can accommodate multiple dimensions of execution quality.
Monetary policy and the private sector behaviour of the U.S. economy are modelled as a time varying structural vector autoregression, where the sources of time variation are both the coefficients and the variance covariance matrix of the innovations. The paper develops a new, simple modelling strategy for the law of motion of the variance covariance matrix and proposes an efficient Markov chain Monte Carlo algorithm for the model likelihood/posterior numerical evaluation. The main empirical conclusions are: (1) both systematic and non-systematic monetary policy have changed during the last 40 years—in particular, systematic responses of the interest rate to inflation and unemployment exhibit a trend toward a more aggressive behaviour, despite remarkable oscillations; (2) this has had a negligible effect on the rest of the economy. The role played by exogenous non-policy shocks seems more important than interest rate policy in explaining the high inflation and unemployment episodes in recent U.S. economic history.
Quarterly Journal of Economics2005120(2), 467-515open access
Forty million people are infected with HIV worldwide; twenty-five million of them are in Sub-Saharan Africa. This paper addresses the question of why Africa has been so heavily affected by HIV, and what explains the variation within Africa. I present a model that decomposes epidemic level into differences in sexual behavior and differences in viral transmission rates. I argue, using evidence drawn from the existing medical literature, that Africa has very high HIV transmission rates, likely due to high rates of other untreated sexually transmitted infections, while transmission rates in the United States are low. The difference in transmission rates is large enough to explain the observed difference in prevalence between the United States and Sub-Saharan Africa. The model also provides a good fit to cross-country data within Africa and suggests that, in contrast to the intra-continental results, differences within that continent can be attributed to differences in sexual behavior and epidemic timing. The results suggest that cost-effective policy interventions would focus on decreasing transmission rates within Africa, possibly by treating other untreated sexually transmitted infections.
Journal of Economic Literature200543(4), 1049-1062
Jared Diamond’s Collapse: How Societies Choose to Fail or Succeed (Viking Penguin, 2005), tells the dramatic decline of past civilizations—the Easter Islanders, the Anasazi in the Southwestern United States, the Mayans in Central America, the Norse Vinland settlement in Greenland. These civilizations did not slowly fall apart; they suffered drastic reductions in population and productivity. In Diamond's account, their collapses result from mismanaged resources, lost friends, gained enemies, climate changes, and most tellingly, their cultures and beliefs. Diamond provides captivating histories and an engaging explanation of the sciences required to piece those histories together, but his logic and his prescriptions would benefit from greater familiarity with some basic principles of economics and a richer understanding of human nature.
The SARS-CoV-2 has been spread to 26 countries around the world since its outbreak. By February 16, 2020, more than 68 000 people had been diagnosed with COVID-19. Researchers from all over the world have carried out timely studies on this public health emergency and produced a number of scientific publications. This review aims to re-analyze and summarize the current research findings in a timely manner to guide scholars in relevant fields to further SARS-CoV-2 research and assist healthcare professionals in their work and decision-making. The SARS-CoV-2 related terms were selected in both English and Chinese and were searched in several major databases, including Pubmed, Web of Science, CNKI, Wanfang, and VIP databases. The reference list of each search result was screened for relevance, which was further supplemented to the search results. The included studies were categorized by topics with key characteristics extracted, re-analyzed, and summarized. A total of 301 articles were finally included with 136 in Chinese and 165 in English. The number of publications has rapidly increased since mid-January, 2020, and a peak day was 6th February on which 50 articles were published. The top three countries publishing articles were China, the United States and the United Kingdom. The Lancet and its specialty journals have published the most articles, with contribution also from journals such as New England Journal of Medicine ( NEJM ), The Journal of the American Medical Association ( JAMA ), and Nature . All articles were categorized into epidemiology, clinical diagnosis and treatment, basic research, pregnant women and children, mental health, epidemic prevention & control, and others. The literatures related to SARS-CoV-2 are emerging rapidly. It is necessary to sort out and summarize the research topic in time, which has a good reference value for staff in different positions. At the same time, it is necessary to strengthen the judgment of the quality of literatures.
This paper develops a model of the interaction between the supply of hate-creating stories from politicians and the willingness of voters to listen to hatred. Hatred is fostered with stories of an out-group's crimes, but the impact of these stories comes from repetition not truth. Hate-creating stories are supplied by politicians when such actions help to discredit opponents whose policies benefit an out-group. Egalitarians foment hatred against rich minorities; opponents of re-distribution build hatred against poor minorities. Hatred relies on people accepting, rather than investigating, hate-creating stories. Hatred declines when there is private incentive to learn the truth. Increased economic interactions with a minority group may provide that incentive. This framework is used to illuminate the evolution of anti-Black hatred in the United States South, episodes of anti-Semitism in Europe, and the recent surge of anti-Americanism in the Arab world.