This essay discusses a new approach to macroeconomics called modern monetary theory (MMT). It identifies the key differences between MMT and the approach found in mainstream textbooks. It concludes that while MMT contains some kernels of truth, its most novel policy prescriptions do not follow cogently from its premises.
{"title":"A Skeptic’s Guide to Modern Monetary Theory","authors":"N. Mankiw","doi":"10.1257/PANDP.20201102","DOIUrl":"https://doi.org/10.1257/PANDP.20201102","url":null,"abstract":"This essay discusses a new approach to macroeconomics called modern monetary theory (MMT). It identifies the key differences between MMT and the approach found in mainstream textbooks. It concludes that while MMT contains some kernels of truth, its most novel policy prescriptions do not follow cogently from its premises.","PeriodicalId":18934,"journal":{"name":"National Bureau of Economic Research","volume":"32 1","pages":"141-144"},"PeriodicalIF":0.0,"publicationDate":"2020-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80242981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Using data from 2018, a number of studies have found that recent U.S tariffs have been passed on entirely to U.S. importers and consumers. These results are surprising given that trade theory has long stressed that tariffs applied by a large country should drive down foreign prices. Using another year of data including significant escalations in the trade war, we find that U.S. tariffs continue to be almost entirely borne by U.S. firms and consumers. We show that the response of import values to the tariffs increases in absolute magnitude over time, consistent with the idea that it takes time for firms to reorganize supply chains. We find heterogeneity in the responses of some sectors, such as steel, where tariffs have caused foreign exporters to drop their prices substantially, enabling them to export relatively more than in sectors where tariff passthrough was complete.
{"title":"Who’s Paying for the US Tariffs? A Longer-Term Perspective","authors":"M. Amiti, S. Redding, David E. Weinstein","doi":"10.1257/PANDP.20201018","DOIUrl":"https://doi.org/10.1257/PANDP.20201018","url":null,"abstract":"Using data from 2018, a number of studies have found that recent U.S tariffs have been passed on entirely to U.S. importers and consumers. These results are surprising given that trade theory has long stressed that tariffs applied by a large country should drive down foreign prices. Using another year of data including significant escalations in the trade war, we find that U.S. tariffs continue to be almost entirely borne by U.S. firms and consumers. We show that the response of import values to the tariffs increases in absolute magnitude over time, consistent with the idea that it takes time for firms to reorganize supply chains. We find heterogeneity in the responses of some sectors, such as steel, where tariffs have caused foreign exporters to drop their prices substantially, enabling them to export relatively more than in sectors where tariff passthrough was complete.","PeriodicalId":18934,"journal":{"name":"National Bureau of Economic Research","volume":"41 1","pages":"541-546"},"PeriodicalIF":0.0,"publicationDate":"2020-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88522664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Property rights are widely prescribed for addressing overextraction of common pool resources, yet causal evidence of their effectiveness remains elusive. We develop a model of dynamic groundwater extraction to demonstrate how a spatial regression discontinuity design exploiting a spatially-incomplete property rights regime recovers a lower bound on the value of property rights. We apply this estimator to a major aquifer in water-scarce southern California and find that the introduction of ground- water property rights generated substantial net benefits, as capitalized in land values. Heterogeneity analyses suggest gains arise in part from tradeability of these rights, which enables more efficient water use.
{"title":"Do Property Rights Alleviate the Problem of the Commons? Evidence from California Groundwater Rights","authors":"A. Ayres, Kyle C. Meng, A. Plantinga","doi":"10.3386/w26268","DOIUrl":"https://doi.org/10.3386/w26268","url":null,"abstract":"Property rights are widely prescribed for addressing overextraction of common pool resources, yet causal evidence of their effectiveness remains elusive. We develop a model of dynamic groundwater extraction to demonstrate how a spatial regression discontinuity design exploiting a spatially-incomplete property rights regime recovers a lower bound on the value of property rights. We apply this estimator to a major aquifer in water-scarce southern California and find that the introduction of ground- water property rights generated substantial net benefits, as capitalized in land values. Heterogeneity analyses suggest gains arise in part from tradeability of these rights, which enables more efficient water use.","PeriodicalId":18934,"journal":{"name":"National Bureau of Economic Research","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90808934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Carrera, Heather Royer, Mark Stehr, Justin R. Sydnor, Dmitry Taubinsky
A large literature treats take-up of commitment contracts, in the form of choice-set restrictions or penalties, as a smoking gun for time-inconsistency or self-control problems (for short, “present focus”). This paper develops techniques for inspecting this assumption, presents new field-experimental results that challenge it, and provides an alternative approach to measuring present focus. Theoretically, we show that in a standard model of quasi-hyperbolic discounting, demand for commitment is unlikely when there is some uncertainty about the future. In a field experiment with 1292 members of a fitness facility, we test for the presence of imperfect perception of contract value and experimenter demand effects in commitment contract take-up by offering contracts both for going to the gym more and for going to the gym less. We find that there is significant take-up of both types of contracts, and that individuals who take up contracts to go to the gym more are the most likely to take up contracts to go the gym less. These starkly conflicting choices are inconsistent with all standard models of present focus, and suggest that offers of commitment contracts may not be well-targeted policy tools. However, we show that a combination of belief forecasts and elicitations of willingness-to-pay for piece-rate incentives provides more robust identification of present focus and people’s awareness of it. We apply the methodology to our experimental results to obtain estimates of the partially sophisticated quasi-hyperbolic discounting model.
{"title":"Who Chooses Commitment? Evidence and Welfare Implications","authors":"M. Carrera, Heather Royer, Mark Stehr, Justin R. Sydnor, Dmitry Taubinsky","doi":"10.3386/W26161","DOIUrl":"https://doi.org/10.3386/W26161","url":null,"abstract":"A large literature treats take-up of commitment contracts, in the form of choice-set restrictions or penalties, as a smoking gun for time-inconsistency or self-control problems (for short, “present focus”). This paper develops techniques for inspecting this assumption, presents new field-experimental results that challenge it, and provides an alternative approach to measuring present focus. Theoretically, we show that in a standard model of quasi-hyperbolic discounting, demand for commitment is unlikely when there is some uncertainty about the future. In a field experiment with 1292 members of a fitness facility, we test for the presence of imperfect perception of contract value and experimenter demand effects in commitment contract take-up by offering contracts both for going to the gym more and for going to the gym less. We find that there is significant take-up of both types of contracts, and that individuals who take up contracts to go to the gym more are the most likely to take up contracts to go the gym less. These starkly conflicting choices are inconsistent with all standard models of present focus, and suggest that offers of commitment contracts may not be well-targeted policy tools. However, we show that a combination of belief forecasts and elicitations of willingness-to-pay for piece-rate incentives provides more robust identification of present focus and people’s awareness of it. We apply the methodology to our experimental results to obtain estimates of the partially sophisticated quasi-hyperbolic discounting model.","PeriodicalId":18934,"journal":{"name":"National Bureau of Economic Research","volume":"114 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79333070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rahi Abouk, Scott Adams, Bo Feng, J. Maclean, M. Pesko
We use the universe of birth records in the United States from 2013 to 2017 to examine the effect of e-cigarette taxes on pre-pregnancy smoking, prenatal smoking, and birth outcomes (birth weight, gestational length, and Apgar 5 score). We apply a differences-in-differences model to study these questions. We have two principle findings. First, e-cigarette tax adoption increases pre-pregnancy and prenatal smoking, implying that e-cigarettes and traditional cigarettes are substitutes among pregnant women. Second, in line with clinical literature suggesting that both e-cigarettes and traditional cigarettes are harmful to developing fetuses, birth outcomes are largely unchanged following adoption of an e-cigarette tax. In sum, our results suggest that e-cigarettes reduce prenatal smoking, but have no observable benefit towards the goal of promoting fetal development.
{"title":"The Effect of E-Cigarette Taxes on Pre-pregnancy and Prenatal Smoking","authors":"Rahi Abouk, Scott Adams, Bo Feng, J. Maclean, M. Pesko","doi":"10.3386/W26126","DOIUrl":"https://doi.org/10.3386/W26126","url":null,"abstract":"We use the universe of birth records in the United States from 2013 to 2017 to examine the effect of e-cigarette taxes on pre-pregnancy smoking, prenatal smoking, and birth outcomes (birth weight, gestational length, and Apgar 5 score). We apply a differences-in-differences model to study these questions. We have two principle findings. First, e-cigarette tax adoption increases pre-pregnancy and prenatal smoking, implying that e-cigarettes and traditional cigarettes are substitutes among pregnant women. Second, in line with clinical literature suggesting that both e-cigarettes and traditional cigarettes are harmful to developing fetuses, birth outcomes are largely unchanged following adoption of an e-cigarette tax. In sum, our results suggest that e-cigarettes reduce prenatal smoking, but have no observable benefit towards the goal of promoting fetal development.","PeriodicalId":18934,"journal":{"name":"National Bureau of Economic Research","volume":"36 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83115163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A mainstream motivation for decentralized government is to enable public service investments to better align with political preferences that may differ by geographical region. This paper examines how political preferences determine local government provision of hospital services. We find that local governments in areas more supportive of public insurance expansion responded to such state action by increasing expenditures on hospitals, whereas those in areas that voted against such expansions used the savings to reduce property taxes. This finding suggests that local government financial responses indeed align with political preferences.
{"title":"Do Local Governments Represent Voter Preferences? Evidence from Hospital Financing under the Affordable Care Act","authors":"Victoria E Perez, J. Ross, K. Simon","doi":"10.3386/W26094","DOIUrl":"https://doi.org/10.3386/W26094","url":null,"abstract":"A mainstream motivation for decentralized government is to enable public service investments to better align with political preferences that may differ by geographical region. This paper examines how political preferences determine local government provision of hospital services. We find that local governments in areas more supportive of public insurance expansion responded to such state action by increasing expenditures on hospitals, whereas those in areas that voted against such expansions used the savings to reduce property taxes. This finding suggests that local government financial responses indeed align with political preferences.","PeriodicalId":18934,"journal":{"name":"National Bureau of Economic Research","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85266475","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-01-01DOI: 10.7208/chicago/9780226633251.001.0001
R. Gallman, P. Rhode
When we think about history, we often think about people, events, ideas, and revolutions, but what about the numbers? What do the data tell us about what was, what is, and how things changed over time? Economist Robert E. Gallman (1926–98) gathered extensive data on US capital stock and created a legacy that has, until now, been difficult for researchers to access and appraise in its entirety. Gallman measured American capital stock from a range of perspectives, viewing it as the accumulation of income saved and invested, and as an input into the production process. He used the level and change in the capital stock as proxy measures for long-run economic performance. Analyzing data in this way from the end of the US colonial period to the turn of the twentieth century, Gallman placed our knowledge of the long nineteenth century—the period during which the United States began to experience per capita income growth and became a global economic leader—on a strong empirical foundation. Gallman’s research was painstaking and his analysis meticulous, but he did not publish the material backing to his findings in his lifetime. Here Paul W. Rhode completes this project, giving permanence to a great economist’s insights and craftsmanship. Gallman’s data speak to the role of capital in the economy, which lies at the heart of many of the most pressing issues today.
当我们想到历史时，我们通常会想到人物、事件、思想和革命，但是数字呢?数据告诉我们什么是过去，什么是现在，以及随着时间的推移，事情是如何变化的?经济学家罗伯特·e·加尔曼(Robert E. Gallman, 1926 - 1998)收集了大量关于美国资本存量的数据，并创造了一项遗产，直到现在，研究人员还难以全面地获取和评估这些数据。Gallman从多个角度衡量了美国的资本存量，将其视为储蓄和投资收入的积累，以及生产过程的投入。他用资本存量的水平和变化作为衡量长期经济表现的替代指标。Gallman以这种方式分析了从美国殖民时期结束到20世纪之交的数据，将我们对漫长的19世纪(美国开始经历人均收入增长并成为全球经济领导者的时期)的认识置于强大的实证基础之上。加尔曼的研究是艰苦的，他的分析是细致的，但他在有生之年没有发表支持他的发现的材料。在这里，保罗·w·罗德完成了这个项目，给了一个伟大的经济学家的洞察力和手艺永久。Gallman的数据说明了资本在经济中的作用，这是当今许多最紧迫问题的核心。
{"title":"Capital in the Nineteenth Century","authors":"R. Gallman, P. Rhode","doi":"10.7208/chicago/9780226633251.001.0001","DOIUrl":"https://doi.org/10.7208/chicago/9780226633251.001.0001","url":null,"abstract":"When we think about history, we often think about people, events, ideas, and revolutions, but what about the numbers? What do the data tell us about what was, what is, and how things changed over time? Economist Robert E. Gallman (1926–98) gathered extensive data on US capital stock and created a legacy that has, until now, been difficult for researchers to access and appraise in its entirety. Gallman measured American capital stock from a range of perspectives, viewing it as the accumulation of income saved and invested, and as an input into the production process. He used the level and change in the capital stock as proxy measures for long-run economic performance. Analyzing data in this way from the end of the US colonial period to the turn of the twentieth century, Gallman placed our knowledge of the long nineteenth century—the period during which the United States began to experience per capita income growth and became a global economic leader—on a strong empirical foundation. Gallman’s research was painstaking and his analysis meticulous, but he did not publish the material backing to his findings in his lifetime. Here Paul W. Rhode completes this project, giving permanence to a great economist’s insights and craftsmanship. Gallman’s data speak to the role of capital in the economy, which lies at the heart of many of the most pressing issues today.","PeriodicalId":18934,"journal":{"name":"National Bureau of Economic Research","volume":"61 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85482822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Social scientists have long sought to examine the causal impact of school spending on child outcomes. For a long time, the literature on this topic was largely descriptive so that it had been difficult to draw strong causal claims. However, there have been several recent studies in this space that employ larger data-sets and use quasi-experimental methods that allow for much more credible causal claims. Focusing on studies of students in the United States, this paper briefly discusses the older literature and highlights some of its limitations. It then describes a recent quasi-experimental literature on the impact of school spending on child outcomes, highlights some key papers, and presents a summary of the recent findings. Policy implications and areas for future research are discussed.
{"title":"Does School Spending Matter? The New Literature on an Old Question","authors":"Kirabo Jackson","doi":"10.3386/W25368","DOIUrl":"https://doi.org/10.3386/W25368","url":null,"abstract":"Social scientists have long sought to examine the causal impact of school spending on child outcomes. For a long time, the literature on this topic was largely descriptive so that it had been difficult to draw strong causal claims. However, there have been several recent studies in this space that employ larger data-sets and use quasi-experimental methods that allow for much more credible causal claims. Focusing on studies of students in the United States, this paper briefly discusses the older literature and highlights some of its limitations. It then describes a recent quasi-experimental literature on the impact of school spending on child outcomes, highlights some key papers, and presents a summary of the recent findings. Policy implications and areas for future research are discussed.","PeriodicalId":18934,"journal":{"name":"National Bureau of Economic Research","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91341997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I unite the economics and medical literatures by examining behavior within a clinical trial to inform treatment guidelines. I use data from the Canadian National Breast Screening Study, an influential clinical trial on mammography. During the active study period of the trial, a substantial fraction of women in the control group received mammograms, and some women in the intervention group did not. Using this mammography behavior, random assignment within the trial, and a standard model from the economics literature, I divide participants into three groups that differ in how likely they are to receive mammograms. Making comparisons across these groups, I find two important relationships. First, I find heterogeneous selection into mammography: women more likely to receive mammograms are healthier. I find this relationship using a marginal treatment effect model that assumes no more than the local average treatment effect assumptions. Second, I find treatment effect heterogeneity along the margin of selection into mammography: women more likely to receive mammograms are more likely to experience harm from them. I find this relationship using an ancillary assumption that builds on the first empirical relationship. I find additional empirical support for the ancillary assumption using baseline covariates. My findings contribute to the literature concerned about harms from mammography by demonstrating variation across the margin of selection into mammography. This variation is problematic for current mammography guidelines for women in their 40s because it implies that they unintentionally encourage mammography for healthier women who are more likely to experience harm from them.
{"title":"Behavior within a Clinical Trial and Implications for Mammography Guidelines","authors":"Amanda E. Kowalski","doi":"10.3386/W25049","DOIUrl":"https://doi.org/10.3386/W25049","url":null,"abstract":"I unite the economics and medical literatures by examining behavior within a clinical trial to inform treatment guidelines. I use data from the Canadian National Breast Screening Study, an influential clinical trial on mammography. During the active study period of the trial, a substantial fraction of women in the control group received mammograms, and some women in the intervention group did not. Using this mammography behavior, random assignment within the trial, and a standard model from the economics literature, I divide participants into three groups that differ in how likely they are to receive mammograms. Making comparisons across these groups, I find two important relationships. First, I find heterogeneous selection into mammography: women more likely to receive mammograms are healthier. I find this relationship using a marginal treatment effect model that assumes no more than the local average treatment effect assumptions. Second, I find treatment effect heterogeneity along the margin of selection into mammography: women more likely to receive mammograms are more likely to experience harm from them. I find this relationship using an ancillary assumption that builds on the first empirical relationship. I find additional empirical support for the ancillary assumption using baseline covariates. My findings contribute to the literature concerned about harms from mammography by demonstrating variation across the margin of selection into mammography. This variation is problematic for current mammography guidelines for women in their 40s because it implies that they unintentionally encourage mammography for healthier women who are more likely to experience harm from them.","PeriodicalId":18934,"journal":{"name":"National Bureau of Economic Research","volume":"132 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82952540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We show that the Diamond and Mirrlees (1971) linear tax model contains the Mirrlees (1971) nonlinear tax model as a special case. In this sense, the Mirrlees model is an application of Diamond-Mirrlees. We also provide a simple derivation of the Mirrleesian optimal income tax formula from the Diamond-Mirrlees commodity tax formula. In the Mirrlees model, the relevant compensated cross-price elasticities are zero, providing a situation where an inverse elasticity rule holds. We provide four extensions that illustrate the power and ease of our approach, based on Diamond-Mirrlees, to study nonlinear taxation. First, we consider annual taxation in a lifecycle context. Second, we include human capital investments. Third, we incorporate more general forms of heterogeneity into the basic Mirrlees model. Fourth, we consider an extensive margin labor force participation decision, alongside the intensive margin choice. In all these cases, the relevant optimality condition is easily obtained as a direct application of the general Diamond-Mirrlees linear tax formula.
{"title":"Mirrlees meets Diamond-Mirrlees: simplifying nonlinear income taxation","authors":"Florian Scheuer, I. Werning","doi":"10.3386/W22076","DOIUrl":"https://doi.org/10.3386/W22076","url":null,"abstract":"We show that the Diamond and Mirrlees (1971) linear tax model contains the Mirrlees (1971) nonlinear tax model as a special case. In this sense, the Mirrlees model is an application of Diamond-Mirrlees. We also provide a simple derivation of the Mirrleesian optimal income tax formula from the Diamond-Mirrlees commodity tax formula. In the Mirrlees model, the relevant compensated cross-price elasticities are zero, providing a situation where an inverse elasticity rule holds. We provide four extensions that illustrate the power and ease of our approach, based on Diamond-Mirrlees, to study nonlinear taxation. First, we consider annual taxation in a lifecycle context. Second, we include human capital investments. Third, we incorporate more general forms of heterogeneity into the basic Mirrlees model. Fourth, we consider an extensive margin labor force participation decision, alongside the intensive margin choice. In all these cases, the relevant optimality condition is easily obtained as a direct application of the general Diamond-Mirrlees linear tax formula.","PeriodicalId":18934,"journal":{"name":"National Bureau of Economic Research","volume":"41 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74203873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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