MILTON FRIEDMAN AND ANNA SCHWARTZ Monetary Trends reports a great many findings-53 are enumerated in the introduction-but paramount is the stability of the demand for money in the US and Britain over the past century. The money stock controls money income. This proposition more than anything else is the point of their painstaking investigation. Friedman and Schwartz argue against what might neutrally be called the early post-war view of the macroeconomic role of money: Velocity will move easily to reconcile any level of nominal income to any money stock. The demand for money in this view is a will-o'the-wisp, as the authors put it. Monetary policy has little influence over real activity; stabilization policy necessarily relies on fiscal instruments. The volume is completely convincing in disposing of this idea; today's reader is likely to be puzzled why so much space is devoted to a view that has no serious adherents among professional economists. Friedman and Schwartz are generals fighting an earlier war, a situation accentuated by the long lags in putting this volume into print. Though the opposing armies fighting for the early postwar view have withdrawn in total rout, a new front has opened up, and the quantity theory is fighting for its life once again. Worse yet, the new armies are fighting under the banner of free-market economics and are led by former colleagues and students of Milton Friedman. The midwest, once the stronghold of the quantity theory, is now largely occupied by the enemy. The new monetary economics views the quantity theory as nothing more than an artifact of government regulation. An economy organized along free-market principles could function without money at all (Fischer Black, 1970). It is true that the kinds of monetary regulations imposed by the American and British governments of the past century create a more-or-less stable relation between a certain class of assets called money and nominal spending (Eugene Fama, 1980), but different regulations would alter that relation. Even the real bills doctrine, anathema to quantity theorists because it invites unlimited expansion of the money supply, has advocates in the new school (Thomas Sargent and Neil Wallace, 1981). monetary system where the government is unconcerned about the money stock has been advocated by a University of Chicago economist while visiting the Hoover Institution (John Bilson, 1981). Restoring the intrinsic value of money, not limiting its quantity, has been found to be the key to successful disinflation by one member of this group (Sargent, 1982). critical summary, titled A Laissez Faire Approach to Monetary Stability, written * See p. 1528, above, for publication information.

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.

I consider three views of the labor market. In the first, wages are flexible and employment follows the principle of bilateral efficiency. Workers never lose their jobs because of sticky wages. In the second, wages are sticky and inefficient layoffs do occur. In the third, wages are also sticky, but employment governance is efficient. I show that the behavior of flows in the labor market strongly favors the third view. In the modern U.S. economy, recessions do not begin with a burst of layoffs. Unemployment rises because jobs are hard to find, not because an unusual number of people are thrown into unemployment.

Excessive layoffs in bad times and excessive quits in good times both stem from the same weakness in practical employment arrangements: the specific nature of worker-firm relations creates a situation of bilateral monopoly. Institutions which have arisen to avert the associated inefficiency cannot mimic the separation decisions of a perfect-information, first-best allocation rule. Simple employment rules based on predetermined or indexed wages are in many cases the most desirable among the class of feasible employment arrangements. More complicated contracts which seem to deal more effectively with turn-over issues either are infeasible because of informational requirements or create adverse incentives on some other dimension.

Unemployment is high when financial discounts are high. In recessions, the stock market falls and all types of investment fall, including employers' investment in job creation. The discount rate implicit in the stock market rises, and discounts for other claims on business income also rise. A higher discount implies a lower present value of the benefit of a new hire to an employer. According to the leading view of unemployment—the Diamond-Mortensen-Pissarides model—when the incentive for job creation falls, the labor market slackens and unemployment rises. Thus high discount rates imply high unemployment.

In a market-clearing economy, declines in demand from one sector do not cause large declines in aggregate output because other sectors expand. The key price mediating the response is the interest rate. A decline in the rate stimulates all categories of spending. But in a low-inflation economy, the room for a decline in the rate is small, because of the notorious lower limit of zero on the nominal interest rate. In the Great Depression, substantial deflation caused the real interest rate to reach high levels. In the Great Slump that began at the end of 2007, low inflation resulted in an only slightly negative real rate when full employment called for a much lower real rate because of declines in demand. Fortunately, the inflation rate hardly responded to conditions in product and labor markets, else deflation might have occurred, with an even higher real interest rate. I concentrate on three closely related sources of declines in demand: the buildup of excess stocks of housing and consumer durables, the corresponding expansion of consumer debt that financed the buildup, and financial frictions that resulted from the decline in real-estate prices.

Following a recession, the aggregate labor market is slack–employment remains below normal and recruiting efforts of employers, as measured by help-wanted advertising and vacancies, are low. A model of matching friction explains the qualitative responses of the labor market to adverse shocks, but requires implausibly large shocks to account for the magnitude of observed fluctuations. The incorporation of wage stickiness vastly increases the sensitivity of the model to driving forces. I develop a new model of the way that wage stickiness affects unemployment. The stickiness arises in an economic equilibrium and satisfies the condition that no worker-employer pair has an unexploited opportunity for mutual improvement. Sticky wages neither interfere with the efficient formation of employment matches nor cause inefficient job loss. Thus the model provides an answer to the fundamental criticism previously directed at sticky-wage models of fluctuations.

Strong and widely accepted evidence shows that the natural rate of unemployment varies over time with substantial amplitude. The frictions in the labor market that account for positive normal levels of unemployment are not simple and mechanical. Instead, as a rich modern body of theory demonstrates, the natural rate of unemployment is an equilibrium in which the volumes of job-seeking by workers and worker-seeking by employers reach a balance controlled by fundamental determinants of the relative prices of the two activities. In recessions, unemployment rises, and job vacancies fall. The natural explanation is an economywide fall in labor demand. But a compelling model that generates a fall in labor demand without a counterfactual fall in productivity has eluded theorists to date. Nonetheless, policymakers have appropriately adopted the view that the natural rate varies over time and is not a simple benchmark for setting monetary instruments.

Economists are as perplexed as anyone by the behavior of the stock market. Figure 1 shows a broad measure of stock-market value in relation to GDP from 1947 through 2000. In addition to saw-tooth movements including the contraction in late 2000, the value of the stock market has large, low-frequency swings, moving upward from 1950 to 1965, then downward to 1982, and upward until early 2000. I entertain the hypothesis that these large movements are the result of rational (if not accurate) appraisal of the cash likely to be received by shareholders in the future. The hypothesis receives some support from work by financial economists showing that irrational markets create profit opportunities for active traders and that passive traders consistently earn higher returns. Most of my discussion will be complementary to the work of financial economists—I will look at the fundamentals underlying stock-market values. The lecture considers three potential contributors to the big movements shown in Figure 1: