One of the important determinants of the response of saving and consumption to the real interest rate is the elasticity of intertemporal substitution. That elasticity can be measured by the response of the rate of change of consumption to changes in the expected real interest rated. A detailed study of data for the twentieth-century United States shows no strong evidence that the elasticity of intertemporal substitution is positive. Earlier findings of substantially positive elasticities are reversed when appropriate estimation methods are used.

[The effects of an unexpected change in income taxes are studied in a model with full rational expectations. In the short run, aggregate supply is quite price elastic because commitments to pay predetermined wages are made 1 or more years in advance. The model also recognizes the limited response of investment to unexpected developments in the short run. The paper finds that much of the effect of unexpected tax policy operates through inflationary expectations--an economy with rational expectations is more responsive to tax changes than is one with naive expectations.]

Optimization of the part of consumers is shown to imply that the marginal utility of consumption evolves according to a random walk with trend. To a reasonable approximation, consumption itself should evolve in the same way. In particular, no variable apart from current consumption should be of any value in predicting future consumption. This implication is tested with time-series data for the postwar United States. It is confirmed for real disposable income, which has no predictive power for consumption, but rejected for an index of stock prices. The paper concludes that the evidence supports a modified version of the life cycle--permanent income hypothesis.

What are the fundamental driving forces of macroeconomic fluctuations? In particular, why do people spend more time working in booms and less in recessions? These are basic questions of macroeconomics. Recent thinking has emphasized technology shifts, preference shifts, and changes in government purchases as likely driving forces. It is useful to distinguish atemporal and intertemporal effects of the driving forces. Under standard assumptions, the technology shift has no effect through atemporal channels because income and substitution effects exactly offset. A straightforward decomposition of movements of employment attributes most of them to the atemporal effects of preference shifts.

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.

To explain the large differences in labor productivity across U.S. states we estimate two models--one based on local geographical externalities and the other on the diversity of local intermediate services--where spatial density results in aggregate increasing returns. Both models lead to a relation between county employment density and productivity at the state level. Using data on gross state output we find that a doubling of employment density increases average labor productivity by around 6 percent. More than half of the variance of output per worker across states can be explained by differences in the density of economic activity.