We use administrative data on the population of New Zealand construction firms from 2001-2012, along with linked data on their employees and working proprietors, to study the relationships among worker flows, entry, and firm productivity. We find that job churn is prevalent in construction, with around 60 percent of firm-worker pairs not existing previously or not existing subsequently. The data also show that firms gaining or losing any labour are more productive than static firms, and that firms gaining labour from other construction firms are 4-6 percent more productive than the industry average in a given year. Our analysis suggests such firms are productive in part because of knowledge flows from other construction firms; in our preferred specification, with firm fixed effects, a standard deviation increase in the productivity of new employees’ previous firms is associated with a 0.6 percent increase in productivity. New entrants are more productive than pre-existing firms. Firms that enter briefly and disappear exhibit high productivity for that brief period, and firms that enter and persist exhibit a persistent productivity advantage that averages about 5%, but which grows as experience accumulates. The entry and worker-knowledge-flow phenomena are distinct, in that the entry effect is not explained by employee composition, and non-entrant firms also benefit from worker knowledge flows.
{"title":"Worker Flows, Entry and Productivity in the New Zealand Construction Industry","authors":"N. Chappell, A. Jaffe, T. Le","doi":"10.29310/WP.2018.02","DOIUrl":"https://doi.org/10.29310/WP.2018.02","url":null,"abstract":"We use administrative data on the population of New Zealand construction firms from 2001-2012, along with linked data on their employees and working proprietors, to study the relationships among worker flows, entry, and firm productivity. We find that job churn is prevalent in construction, with around 60 percent of firm-worker pairs not existing previously or not existing subsequently. The data also show that firms gaining or losing any labour are more productive than static firms, and that firms gaining labour from other construction firms are 4-6 percent more productive than the industry average in a given year. Our analysis suggests such firms are productive in part because of knowledge flows from other construction firms; in our preferred specification, with firm fixed effects, a standard deviation increase in the productivity of new employees’ previous firms is associated with a 0.6 percent increase in productivity. New entrants are more productive than pre-existing firms. Firms that enter briefly and disappear exhibit high productivity for that brief period, and firms that enter and persist exhibit a persistent productivity advantage that averages about 5%, but which grows as experience accumulates. The entry and worker-knowledge-flow phenomena are distinct, in that the entry effect is not explained by employee composition, and non-entrant firms also benefit from worker knowledge flows.","PeriodicalId":325993,"journal":{"name":"Ewing Marion Kauffman Foundation Research Paper Series","volume":"401 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121804389","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}
Martin Beraja, A. Fuster, Erik Hurst, Joseph Vavra
We argue that the time-varying regional distribution of housing equity influences the aggregate consequences of monetary policy through its effects on mortgage refinancing. Using detailed loan-level data, we show that regional differences in housing equity affect refinancing and spending responses to interest rate cuts but that these effects vary over time with changes in the regional distribution of house price growth. We then build a heterogeneous household model of refinancing with both mortgage borrowers and lenders and use it to explore the aggregate implications for monetary policy arising from our regional evidence. We find that the 2008 equity distribution made spending in depressed regions less responsive to interest rate cuts, thus dampening aggregate stimulus and increasing regional consumption inequality, whereas the opposite occurred in some earlier recessions. Taken together, our results strongly suggest that monetary policy makers should track the regional distribution of equity over time.
{"title":"Regional Heterogeneity and the Refinancing Channel of Monetary Policy","authors":"Martin Beraja, A. Fuster, Erik Hurst, Joseph Vavra","doi":"10.2139/ssrn.2619932","DOIUrl":"https://doi.org/10.2139/ssrn.2619932","url":null,"abstract":"We argue that the time-varying regional distribution of housing equity influences the aggregate consequences of monetary policy through its effects on mortgage refinancing. Using detailed loan-level data, we show that regional differences in housing equity affect refinancing and spending responses to interest rate cuts but that these effects vary over time with changes in the regional distribution of house price growth. We then build a heterogeneous household model of refinancing with both mortgage borrowers and lenders and use it to explore the aggregate implications for monetary policy arising from our regional evidence. We find that the 2008 equity distribution made spending in depressed regions less responsive to interest rate cuts, thus dampening aggregate stimulus and increasing regional consumption inequality, whereas the opposite occurred in some earlier recessions. Taken together, our results strongly suggest that monetary policy makers should track the regional distribution of equity over time.","PeriodicalId":325993,"journal":{"name":"Ewing Marion Kauffman Foundation Research Paper Series","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115383500","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}
Daniel W. Elfenbein, Raymond J. Fisman, Brian McManus
We study cheap talk by firms and responses by their consumers, focusing on unverifiable promises of charitable donations on eBay during 2005–2006. Cheap talk listings have lower sales probabilities but sell at higher prices when successful. The negative relationship between cheap talk and sales is concentrated in the months following Hurricane Katrina, a time when verifiable and unverifiable charity listings increased dramatically. Finally, we show that cheap talk sellers have lower quality ratings than those making verifiable donations. Our results suggest that buyers ( justifiably) avoid cheap talk listings when credible quality signals are available, thus limiting the extent of cheap talk. (JEL D12, D82, D83, L15, L31, M31)
{"title":"Does Cheap Talk Affect Market Outcomes? Evidence from Ebay","authors":"Daniel W. Elfenbein, Raymond J. Fisman, Brian McManus","doi":"10.3386/W24437","DOIUrl":"https://doi.org/10.3386/W24437","url":null,"abstract":"We study cheap talk by firms and responses by their consumers, focusing on unverifiable promises of charitable donations on eBay during 2005–2006. Cheap talk listings have lower sales probabilities but sell at higher prices when successful. The negative relationship between cheap talk and sales is concentrated in the months following Hurricane Katrina, a time when verifiable and unverifiable charity listings increased dramatically. Finally, we show that cheap talk sellers have lower quality ratings than those making verifiable donations. Our results suggest that buyers ( justifiably) avoid cheap talk listings when credible quality signals are available, thus limiting the extent of cheap talk. (JEL D12, D82, D83, L15, L31, M31)","PeriodicalId":325993,"journal":{"name":"Ewing Marion Kauffman Foundation Research Paper Series","volume":"101 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116342441","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 examine the interaction of economic and policy uncertainty in a dynamic, heterogeneous firms model. Uncertainty about foreign income, trade protection and their interaction dampens export investment. This can be mitigated by trade agreements, which are particularly valuable in periods of increased demand volatility. We use firm data to establish new facts about U.S. export dynamics in 2003-2011 and estimate the model. We find a significant role for uncertainty in explaining the trade collapse in the 2008 crisis and partial recovery in its aftermath. Consistent with the model predictions, we find that the negative effects worked (1) through the extensive margin, (2) in destinations without preferential agreements with the U.S. (accounting for over half its trade) and (3) in industries with higher potential protection. U.S. exports to non-preferential markets would have been 6.5% higher under an agreement—equivalent to an 8% foreign GDP increase. These findings highlight and quantify the value of international policy commitments through agreements that mitigate uncertainty, particularly during downturns.
{"title":"Economic and Policy Uncertainty: Export Dynamics and the Value of Agreements","authors":"Jeronimo Carballo, Kyle Handley, N. Limão","doi":"10.2139/ssrn.3199943","DOIUrl":"https://doi.org/10.2139/ssrn.3199943","url":null,"abstract":"We examine the interaction of economic and policy uncertainty in a dynamic, heterogeneous firms model. Uncertainty about foreign income, trade protection and their interaction dampens export investment. This can be mitigated by trade agreements, which are particularly valuable in periods of increased demand volatility. We use firm data to establish new facts about U.S. export dynamics in 2003-2011 and estimate the model. We find a significant role for uncertainty in explaining the trade collapse in the 2008 crisis and partial recovery in its aftermath. Consistent with the model predictions, we find that the negative effects worked (1) through the extensive margin, (2) in destinations without preferential agreements with the U.S. (accounting for over half its trade) and (3) in industries with higher potential protection. U.S. exports to non-preferential markets would have been 6.5% higher under an agreement—equivalent to an 8% foreign GDP increase. These findings highlight and quantify the value of international policy commitments through agreements that mitigate uncertainty, particularly during downturns.","PeriodicalId":325993,"journal":{"name":"Ewing Marion Kauffman Foundation Research Paper Series","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128559278","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}
Bernhard Ganglmair, Timothy S. Simcoe, E. Tarantino
The paper studies a dynamic model of the decision to continue or abandon a research project. Researchers improve their ideas over time and also learn whether those ideas will be adopted by the scientific community. Projects are abandoned as researchers grow more pessimistic about their chance of success. It estimates the structural parameters of this dynamic decision problem using a novel data set that contains information on both successful and abandoned projects submitted to the Internet Engineering Task Force (IETF), an organization that creates and maintains internet standards. Using the model and parameter estimates, it also simulates two counterfactual policies: a cost-subsidy and a prize-based incentive scheme. For a fixed budget, subsidies have a larger impact on research output, but prizes perform better when accounting for researchers’ opportunity costs.
{"title":"Learning When to Quit: An Empirical Model of Experimentation","authors":"Bernhard Ganglmair, Timothy S. Simcoe, E. Tarantino","doi":"10.3386/W24358","DOIUrl":"https://doi.org/10.3386/W24358","url":null,"abstract":"The paper studies a dynamic model of the decision to continue or abandon a research project. Researchers improve their ideas over time and also learn whether those ideas will be adopted by the scientific community. Projects are abandoned as researchers grow more pessimistic about their chance of success. It estimates the structural parameters of this dynamic decision problem using a novel data set that contains information on both successful and abandoned projects submitted to the Internet Engineering Task Force (IETF), an organization that creates and maintains internet standards. Using the model and parameter estimates, it also simulates two counterfactual policies: a cost-subsidy and a prize-based incentive scheme. For a fixed budget, subsidies have a larger impact on research output, but prizes perform better when accounting for researchers’ opportunity costs.","PeriodicalId":325993,"journal":{"name":"Ewing Marion Kauffman Foundation Research Paper Series","volume":"95 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124081048","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}
In October 2010, the state government of Andhra Pradesh, India, issued an emergency ordinance, bringing microfinance activities in the state to a complete halt and causing a nationwide shock to the liquidity of lenders, especially those with loans in the affected state. We use this massive dislocation in the microfinance market to identify the causal impacts of a reduction in credit supply on consumption, earnings, and employment in general equilibrium in rural labor markets. Using a proprietary district-level data set from 25 separate, for-profit microlenders matched with household data from the National Sample Survey, we find that district-level reductions in credit supply are associated with significant decreases in casual daily wages, household wage earnings, and consumption. We find a substantial consumption multiplier from credit that is likely driven by two channels—aggregate demand and business investment. We calibrate a simple two-period, two-sector model of the rural economy that incorporates both channels and show that the magnitude of our wage results is consistent with the model’s predictions.
{"title":"Measuring the Equilibrium Impacts of Credit: Evidence from the Indian Microfinance Crisis","authors":"Emily Breza, Cynthia Kinnan","doi":"10.3386/W24329","DOIUrl":"https://doi.org/10.3386/W24329","url":null,"abstract":"\u0000 In October 2010, the state government of Andhra Pradesh, India, issued an emergency ordinance, bringing microfinance activities in the state to a complete halt and causing a nationwide shock to the liquidity of lenders, especially those with loans in the affected state. We use this massive dislocation in the microfinance market to identify the causal impacts of a reduction in credit supply on consumption, earnings, and employment in general equilibrium in rural labor markets. Using a proprietary district-level data set from 25 separate, for-profit microlenders matched with household data from the National Sample Survey, we find that district-level reductions in credit supply are associated with significant decreases in casual daily wages, household wage earnings, and consumption. We find a substantial consumption multiplier from credit that is likely driven by two channels—aggregate demand and business investment. We calibrate a simple two-period, two-sector model of the rural economy that incorporates both channels and show that the magnitude of our wage results is consistent with the model’s predictions.","PeriodicalId":325993,"journal":{"name":"Ewing Marion Kauffman Foundation Research Paper Series","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131550870","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}
Machine learning (ML) and artificial intelligence (AI) have been around for many years. However, in the last 5 years, remarkable progress has been made using multilayered neural networks in diverse areas such as image recognition, speech recognition, and machine translation. AI is a general purpose technology that is likely to impact many industries. In this chapter I consider how machine learning availability might affect the industrial organization of both firms that provide AI services and industries that adopt AI technology. My intent is not to provide an extensive overview of this rapidly-evolving area, but instead to provide a short summary of some of the forces at work and to describe some possible areas for future research.
{"title":"Artificial Intelligence, Economics, and Industrial Organization","authors":"H. Varian","doi":"10.3386/W24839","DOIUrl":"https://doi.org/10.3386/W24839","url":null,"abstract":"Machine learning (ML) and artificial intelligence (AI) have been around for many years. However, in the last 5 years, remarkable progress has been made using multilayered neural networks in diverse areas such as image recognition, speech recognition, and machine translation. AI is a general purpose technology that is likely to impact many industries. In this chapter I consider how machine learning availability might affect the industrial organization of both firms that provide AI services and industries that adopt AI technology. My intent is not to provide an extensive overview of this rapidly-evolving area, but instead to provide a short summary of some of the forces at work and to describe some possible areas for future research.","PeriodicalId":325993,"journal":{"name":"Ewing Marion Kauffman Foundation Research Paper Series","volume":"190 5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128364530","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}
Research Summary: This paper investigates the interaction effects of specialization and relational capital on performance. We distinguish between upstream and downstream relational capital and theorize that higher levels of specialization will buffer against decreases in upstream relational capital, because of deeper domain expertise and stronger downstream relational capital. Conversely, higher levels of generalization permit greater gains from increases in upstream relational capital, due to leverage across a more diversified downstream portfolio of activities. We test and find support for these hypotheses in the context of the US lobbying industry. Our study contributes to the strategic human capital literature by isolating the dimension of specialization and relational capital embodied within individuals and providing performance implications of the interactions. Managerial Summary: Both “what you know” and “whom you know” impacts performance. Generalists and specialists are different on the “what you know” dimension. On the “who you know” dimension, we distinguish between upstream (supplier) and downstream (client) relationships. We show that specialists are buffered by deeper downstream relations from performance declines when their powerful upstream connections lose power. Generalists benefit from broader networks when their upstream connections gain power. Thus, when the value of their relationships change, specialists and generalists should each assess when they can reap performance benefits, and when they need to bolster against adversities. For firms, our study suggests hiring the right mix of specialists and generalists is important to reduce risks from relational losses while enjoying the performance benefits from relational gains.
{"title":"Leveraging Who You Know by What You Know: Specialization and Returns to Relational Capital","authors":"Heejung Byun, J. Frake, Rajshree Agarwal","doi":"10.1002/SMJ.2790","DOIUrl":"https://doi.org/10.1002/SMJ.2790","url":null,"abstract":"Research Summary: This paper investigates the interaction effects of specialization and relational capital on performance. We distinguish between upstream and downstream relational capital and theorize that higher levels of specialization will buffer against decreases in upstream relational capital, because of deeper domain expertise and stronger downstream relational capital. Conversely, higher levels of generalization permit greater gains from increases in upstream relational capital, due to leverage across a more diversified downstream portfolio of activities. We test and find support for these hypotheses in the context of the US lobbying industry. Our study contributes to the strategic human capital literature by isolating the dimension of specialization and relational capital embodied within individuals and providing performance implications of the interactions. Managerial Summary: Both “what you know” and “whom you know” impacts performance. Generalists and specialists are different on the “what you know” dimension. On the “who you know” dimension, we distinguish between upstream (supplier) and downstream (client) relationships. We show that specialists are buffered by deeper downstream relations from performance declines when their powerful upstream connections lose power. Generalists benefit from broader networks when their upstream connections gain power. Thus, when the value of their relationships change, specialists and generalists should each assess when they can reap performance benefits, and when they need to bolster against adversities. For firms, our study suggests hiring the right mix of specialists and generalists is important to reduce risks from relational losses while enjoying the performance benefits from relational gains.","PeriodicalId":325993,"journal":{"name":"Ewing Marion Kauffman Foundation Research Paper Series","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122147796","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}
This paper explores the international dimensions of the economics of artificial intelligence. Trade theory emphasizes the roles of scale, competition, and knowledge creation and knowledge diffusion as fundamental to comparative advantage. We explore key features of AI with respect to these dimensions and describe the features of an appropriate model of international trade in the context of AI. We then discuss policy implications with respect to investments in research, and behind-the-border regulations such as privacy, data localization, standards, and competition. We conclude by emphasizing that there is still much to learn before we have a comprehensive understanding of how AI will affect trade.
{"title":"Ai and International Trade","authors":"Avi Goldfarb, Daniel Trefler","doi":"10.3386/W24254","DOIUrl":"https://doi.org/10.3386/W24254","url":null,"abstract":"This paper explores the international dimensions of the economics of artificial intelligence. Trade theory emphasizes the roles of scale, competition, and knowledge creation and knowledge diffusion as fundamental to comparative advantage. We explore key features of AI with respect to these dimensions and describe the features of an appropriate model of international trade in the context of AI. We then discuss policy implications with respect to investments in research, and behind-the-border regulations such as privacy, data localization, standards, and competition. We conclude by emphasizing that there is still much to learn before we have a comprehensive understanding of how AI will affect trade.","PeriodicalId":325993,"journal":{"name":"Ewing Marion Kauffman Foundation Research Paper Series","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129276936","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 : 2017-11-14DOI: 10.1108/S1074-754020170000019002
J. Tyler, E. Absher, K. Garman, Anthony J. Luppino
Abstract This chapter demonstrates that social business models do not meaningfully prioritize or impose accountability to “social good” over other purposes in ways that (a) best protect against owners changing their minds or entry of new owners with different priorities and (b) enable reliable accountability over time and across circumstances. This chapter further suggests a model – a “social primacy company” – that actually prioritizes “social good” and meaningful accountability to it. This chapter thus clarifies circumstances under which existing models might be most useful and are not particularly useful, especially as investors, entrepreneurs, employees, regulators, and others pursue shared, common understandings about purposes, priorities, and accountability.
{"title":"Purposes, Priorities and Accountability Under Social Business Structures: Resolving Ambiguities and Enhancing Adoption","authors":"J. Tyler, E. Absher, K. Garman, Anthony J. Luppino","doi":"10.1108/S1074-754020170000019002","DOIUrl":"https://doi.org/10.1108/S1074-754020170000019002","url":null,"abstract":"Abstract This chapter demonstrates that social business models do not meaningfully prioritize or impose accountability to “social good” over other purposes in ways that (a) best protect against owners changing their minds or entry of new owners with different priorities and (b) enable reliable accountability over time and across circumstances. This chapter further suggests a model – a “social primacy company” – that actually prioritizes “social good” and meaningful accountability to it. This chapter thus clarifies circumstances under which existing models might be most useful and are not particularly useful, especially as investors, entrepreneurs, employees, regulators, and others pursue shared, common understandings about purposes, priorities, and accountability.","PeriodicalId":325993,"journal":{"name":"Ewing Marion Kauffman Foundation Research Paper Series","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129625688","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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