Kaj bi makroekonomisti morali raziskovati

Janet Yellen, predsednica Fed, je prejšnji petek imela zelo odmeven govor o tem, kam bi makroekonomisti morali usmeriti svoj raziskovalni fokus. Naštela je štiri področja. Kot prvo je navedla vpliv agregatnega povpraševanja na agregatno ponudbo. To je seveda v nasprotju z dosedanjo doktrino, kjer so dolgoročni BDP determinirali faktorji na strani ponudbe, medtem ko je bilo povpraševanju dopuščeno zgolj vplivanje na ciklično nihanje okrog trendne dinamike BDP. Zadnje raziskave, predvsem Summers & Fatas (2016), pa so pokazale, da recesije (padec povpraševanja) puščajo globoke rane tudi v dolgoročnem BDP, saj zaradi učinka histereze del delovne sile in kapitala ostane trajno nezaposlen.

Drugo področje je obravnava agentov v makro modelih. Yellenova pravilno pravi, da bi morali opustiti predpostavko reprezentativnega agenta in preiti na heterogene agente, saj en sam reprezentativni agent slabo oziroma napačno prikazuje dejansko stanje. Tretje področje je interakcija med finančnim in realnim sektorjem, predvsem vpliv povečanega zasebnega dolga na fluktuacije BDP. Kot zadnje pa navaja raziskovanje vzrokov za inflacijo, kjer se je stara paradigma glede vpliva plač in kratkoročnih inflacijskih pričakovanj izpela.

Spodaj nekaj odlomkov iz govora Yellenove.

The Influence of Demand on Aggregate Supply
The first question I would like to pose concerns the distinction between aggregate supply and aggregate demand: Are there circumstances in which changes in aggregate demand can have an appreciable, persistent effect on aggregate supply?

Prior to the Great Recession, most economists would probably have answered this question with a qualified “no.” They would have broadly agreed with Robert Solow that economic output over the longer term is primarily driven by supply–the amount of output of goods and services the economy is capable of producing, given its labor and capital resources and existing technologies. Aggregate demand, in contrast, was seen as explaining shorter-term fluctuations around the mostly exogenous supply-determined longer-run trend.1 This conclusion deserves to be reconsidered in light of the failure of the level of economic activity to return to its pre-recession trend in most advanced economies. This post-crisis experience suggests that changes in aggregate demand may have an appreciable, persistent effect on aggregate supply–that is, on potential output.2

The idea that persistent shortfalls in aggregate demand could adversely affect the supply side of the economy–an effect commonly referred to as hysteresis–is not new; for example, the possibility was discussed back in the mid-1980s with regard to the performance of European labor markets.3 But interest in the topic has increased in light of the persistent slowdown in economic growth seen in many developed economies since the crisis. Several recent studies present cross-country evidence indicating that severe and persistent recessions have historically had these sorts of long-term effects, even for downturns that appear to have resulted largely or entirely from a shock to aggregate demand.4 With regard to the U.S. experience, one study estimates that the level of potential output is now 7 percent below what would have been expected based on its pre-crisis trajectory, and it argues that much of this supply-side damage is attributable to several developments that likely occurred as a result of the deep recession and slow recovery.5 In particular, the study finds that in the wake of the crisis, the United States experienced a modest reduction in labor supply as a result of reduced immigration and a fall in labor force participation beyond what can be explained by cyclical conditions and demographic factors, as well as a marked slowdown in the estimated trend growth rate of labor productivity. The latter likely reflects an unusually slow pace of business capital accumulation since the crisis and, more conjecturally, the sharp decline in spending on research and development and the very slow pace of new firm formation in recent years.6

If we assume that hysteresis is in fact present to some degree after deep recessions, the natural next question is to ask whether it might be possible to reverse these adverse supply-side effects by temporarily running a “high-pressure economy,” with robust aggregate demand and a tight labor market. One can certainly identify plausible ways in which this might occur. Increased business sales would almost certainly raise the productive capacity of the economy by encouraging additional capital spending, especially if accompanied by reduced uncertainty about future prospects. In addition, a tight labor market might draw in potential workers who would otherwise sit on the sidelines and encourage job-to-job transitions that could also lead to more-efficient–and, hence, more-productive–job matches.7 Finally, albeit more speculatively, strong demand could potentially yield significant productivity gains by, among other things, prompting higher levels of research and development spending and increasing the incentives to start new, innovative businesses.

Hysteresis effects–and the possibility they might be reversed–could have important implications for the conduct of monetary and fiscal policy. For example, hysteresis would seem to make it even more important for policymakers to act quickly and aggressively in response to a recession, because doing so would help to reduce the depth and persistence of the downturn, thereby limiting the supply-side damage that might otherwise ensue. In addition, if strong economic conditions can partially reverse supply-side damage after it has occurred, then policymakers may want to aim at being more accommodative during recoveries than would be called for under the traditional view that supply is largely independent of demand.

More research is needed, however, to better understand the influence of movements in aggregate demand on aggregate supply.8 From a policy perspective, we of course need to bear in mind that an accommodative monetary stance, if maintained too long, could have costs that exceed the benefits by increasing the risk of financial instability or undermining price stability. More generally, the benefits and potential costs of pursuing such a strategy remain hard to quantify, and other policies might be better suited to address damage to the supply side of the economy.

My second question asks whether individual differences within broad groups of actors in the economy can influence aggregate economic outcomes–in particular, what effect does such heterogeneity have on aggregate demand?

Many macroeconomists work with models where groups of individual actors, such as households or firms, are treated as a single “representative” agent whose behavior stands in for that of the group as a whole. For example, rather than explicitly modeling and then adding up the separate actions of a large number of different households, a macro model might instead assume that the behavior of a single “average” household can describe the aggregate behavior of all households.

Prior to the financial crisis, these so-called representative-agent models were the dominant paradigm for analyzing many macroeconomic questions. However, a disaggregated approach seems needed to understand some key aspects of the Great Recession. To give one example, consider the effects of negative housing equity on consumption. Although households typically reduce their spending in response to wealth declines, the many households whose equity positions in their homes were actually driven negative by the reduction in house prices may have curtailed their spending even more sharply because of a markedly reduced ability to borrow. Such a development, in turn, would shift the relationship between housing equity (which remained solidly positive in the aggregate) and consumer spending for the economy as a whole. Such a shift in an aggregate relationship would be difficult to understand or predict without using disaggregated data and models.

More generally, studying the effects of household and firm heterogeneity might help us better account for the severity of the recession and the slow recovery. At the household level, recent research finds that heterogeneity can amplify the effects of adverse shocks, a result that is largely driven by households with very little net worth that sharply increase their savings in a recession.9 At the firm level, there is evidence that financial constraints had a particularly large adverse effect on employment at small firms and the start-up of new firms, factors that may be part of the explanation for the Great Recession’s long duration and the subsequent slow recovery.10 More generally, if larger firms seeking to expand have better access to credit than smaller ones, overall growth in investment and employment could depend in part on the distribution of sales across different types of businesses. Modeling any of these issues quantitatively will likely require the use of a heterogeneous-agent framework.

Economists’ understanding of how changes in fiscal and monetary policy affect the economy might also benefit from the recognition that households and firms are heterogeneous. For example, in simple textbook models of the monetary transmission mechanism, central banks operate largely through the effect of real interest rates on consumption and investment. Once heterogeneity is taken into account, other important channels emerge. For example, spending by many households and firms appears to be quite sensitive to changes in labor income, business sales, or the value of collateral that in turn affects their access to credit–conditions that monetary policy affects only indirectly. Studying monetary models with heterogeneous agents more closely could help us shed new light on these aspects of the monetary transmission mechanism.

While the economics profession has long been aware that these issues matter, their effects had been incorporated into macro models only to a very limited extent prior to the financial crisis.11 I am glad to now see a greater emphasis on the possible macroeconomic consequences of heterogeneity, including in work by economists at the Federal Reserve.12 Nevertheless, the various linkages between heterogeneity and aggregate demand are not yet well understood, either empirically or theoretically. More broadly, even though the tools of monetary policy are generally not well suited to achieve distributional objectives, it is important for policymakers to understand and monitor the effects of macroeconomic developments on different groups within society.

Vir: Janet Yellen, Macroeconomic Research After the Crisis

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