Justin V. Hastings, Sarah G. Phillips, David Ubilava, A. Vasnev
How integrated are agricultural markets in conflict-affected states? We answer this question by examining the dynamics of monthly price series of rice, maize and sorghum across eleven cities (markets) of Somalia. Using conflict as a source of transaction costs between spatially connected markets, we examine its role in price transmission between the markets in a panel smooth transition regression framework. We find that in the case of rice—an imported cereal grain—conflict tends to reduce the speed of price transmission between markets. By contrast, we find no evidence of conflict-related transaction costs in the case of maize and sorghum—commodities that are locally produced, particularly in the central and southern parts of Somalia. In all instances, we find that there is some degree of spatial integration among cereal markets around the country, perhaps partly due to informal institutions that can bridge the divides created by conflict, distance and internal political fragmentation. These findings add crucial detail to the literature concerned with the role of commodity prices on poverty and food security in conflict-affected states.
{"title":"Price Transmission in Conflict-Affected States: Evidence from Cereal Markets of Somalia","authors":"Justin V. Hastings, Sarah G. Phillips, David Ubilava, A. Vasnev","doi":"10.1093/jae/ejab012","DOIUrl":"https://doi.org/10.1093/jae/ejab012","url":null,"abstract":"\u0000 How integrated are agricultural markets in conflict-affected states? We answer this question by examining the dynamics of monthly price series of rice, maize and sorghum across eleven cities (markets) of Somalia. Using conflict as a source of transaction costs between spatially connected markets, we examine its role in price transmission between the markets in a panel smooth transition regression framework. We find that in the case of rice—an imported cereal grain—conflict tends to reduce the speed of price transmission between markets. By contrast, we find no evidence of conflict-related transaction costs in the case of maize and sorghum—commodities that are locally produced, particularly in the central and southern parts of Somalia. In all instances, we find that there is some degree of spatial integration among cereal markets around the country, perhaps partly due to informal institutions that can bridge the divides created by conflict, distance and internal political fragmentation. These findings add crucial detail to the literature concerned with the role of commodity prices on poverty and food security in conflict-affected states.","PeriodicalId":51524,"journal":{"name":"Journal of African Economies","volume":"1 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60897310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"经济学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The focus of this paper is the low observed mean consumption elasticity of poverty in Africa, and the suggestion that polarisation of national distributions, specifically the non-parametric ‘relative distribution’ method, is essential to understand the low regional elasticity. The version of the methodology adopted results in a measure of absolute polarisation. We show that the results obtained for 24 countries in the region are entirely a product of this choice, and while preference for translation invariance is a normative matter, claims regarding changes in distributions are not. There is no evidence of distributional changes unaccounted for by standard measures of inequality and mean consumption. These variables also explain the evolution of poverty levels in the 24-country sample. Given that changes in mean consumption and inequality account for both the changes in the chosen measure of polarisation and the evolution of poverty, there is no distinct role for the chosen measure of polarisation in accounting for the evolution of poverty in the region.
{"title":"Polarisation and Poverty Reduction in Africa: The Devil Is in the Choice of Equivalence Relation","authors":"Fraser C. Partridge","doi":"10.1093/JAE/EJAB009","DOIUrl":"https://doi.org/10.1093/JAE/EJAB009","url":null,"abstract":"\u0000 The focus of this paper is the low observed mean consumption elasticity of poverty in Africa, and the suggestion that polarisation of national distributions, specifically the non-parametric ‘relative distribution’ method, is essential to understand the low regional elasticity. The version of the methodology adopted results in a measure of absolute polarisation. We show that the results obtained for 24 countries in the region are entirely a product of this choice, and while preference for translation invariance is a normative matter, claims regarding changes in distributions are not. There is no evidence of distributional changes unaccounted for by standard measures of inequality and mean consumption. These variables also explain the evolution of poverty levels in the 24-country sample. Given that changes in mean consumption and inequality account for both the changes in the chosen measure of polarisation and the evolution of poverty, there is no distinct role for the chosen measure of polarisation in accounting for the evolution of poverty in the region.","PeriodicalId":51524,"journal":{"name":"Journal of African Economies","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46701755","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"经济学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Rossignoli, Mario A. Maggioni, Sara Balestri, Simona Beretta
This paper provides new evidence on the effect of an International Child Support (ICS) program, implemented in ten primary schools located in the outskirts of Goma (Congo, DR), on school performances. Using original micro data in a sample of 309 children (121 treated and 188 control), we explore whether the ICS program impacts on a broad set of alternative educational outcomes - namely, performance scores in 4 different subjects (plus total score), failure rates and school drop-out rates - through a Difference-in-Differences approach. The results show that sponsored children report lower drop-out rates and failure rates with respect to their control peers and, while lagging behind before the program started, in two school years they catch-up in all subjects. Results are robust to the implementation of Coarsened Exact Matching that exploits the structure of the data to produce unbiased estimates along with bounded ex-post balancing.
{"title":"International Child Sponsorship Improves School Performance: Evidence from Goma (DRC)","authors":"D. Rossignoli, Mario A. Maggioni, Sara Balestri, Simona Beretta","doi":"10.1093/JAE/EJAB007","DOIUrl":"https://doi.org/10.1093/JAE/EJAB007","url":null,"abstract":"This paper provides new evidence on the effect of an International Child Support (ICS) program, implemented in ten primary schools located in the outskirts of Goma (Congo, DR), on school performances. Using original micro data in a sample of 309 children (121 treated and 188 control), we explore whether the ICS program impacts on a broad set of alternative educational outcomes - namely, performance scores in 4 different subjects (plus total score), failure rates and school drop-out rates - through a Difference-in-Differences approach. The results show that sponsored children report lower drop-out rates and failure rates with respect to their control peers and, while lagging behind before the program started, in two school years they catch-up in all subjects. Results are robust to the implementation of Coarsened Exact Matching that exploits the structure of the data to produce unbiased estimates along with bounded ex-post balancing.","PeriodicalId":51524,"journal":{"name":"Journal of African Economies","volume":"1 1","pages":"1-26"},"PeriodicalIF":1.6,"publicationDate":"2021-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48035537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"经济学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper examines the effect of experiencing a research collaboration between African scientists and their international partners on the African scientists’ research impact, measured by scores based on the number of citations and journal impact factor. Using a difference-in-difference regression analysis on publication data of African scientists, the results show that international research collaboration in a given year has a positive and significant effect on research impact, which lasts in the subsequent years. The presence of such permanent effect suggests a sort of ‘permanent learning by international collaboration’. The positive effect of international collaboration on research impact, however, does not necessarily imply that the scientists with only local research collaboration are lesser scientists.
{"title":"Does Experiencing International Research Collaboration Permanently Affect the Impact of Scientific Production? Evidence from Africa","authors":"Seyed Reza Mirnezami, C. Beaudry","doi":"10.1093/JAE/EJAB008","DOIUrl":"https://doi.org/10.1093/JAE/EJAB008","url":null,"abstract":"\u0000 This paper examines the effect of experiencing a research collaboration between African scientists and their international partners on the African scientists’ research impact, measured by scores based on the number of citations and journal impact factor. Using a difference-in-difference regression analysis on publication data of African scientists, the results show that international research collaboration in a given year has a positive and significant effect on research impact, which lasts in the subsequent years. The presence of such permanent effect suggests a sort of ‘permanent learning by international collaboration’. The positive effect of international collaboration on research impact, however, does not necessarily imply that the scientists with only local research collaboration are lesser scientists.","PeriodicalId":51524,"journal":{"name":"Journal of African Economies","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41735077","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"经济学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Clementi, Michele Fabiani, Vasco Molini, Rocco Zizzamia
The development path of Sub-Saharan Africa (SSA) over the past two decades has been characterized by sluggish poverty reduction occurring alongside robust economic growth. Applying polarization measures to comparable survey data from 24 SSA countries, we find that there has been a generalizable increase in polarization over the past two decades—and in particular, an increased concentration of households in the lower tail of the welfare distribution of SSA countries. The polarization process is further analyzed by identifying the main drivers and singling out the effect of different covariates at different points in the consumption distribution. This investigation reveals that the drivers of polarization are relatively similar across SSA: demographic, urban/rural, regional variables and access to basic infrastructure are found to be the most important drivers of polarization in many countries.
{"title":"Are We Really Painting the Devil on the Walls? Polarization and its Drivers in Sub-Saharan Africa in the Past Two Decades","authors":"F. Clementi, Michele Fabiani, Vasco Molini, Rocco Zizzamia","doi":"10.1093/JAE/EJAB006","DOIUrl":"https://doi.org/10.1093/JAE/EJAB006","url":null,"abstract":"\u0000 The development path of Sub-Saharan Africa (SSA) over the past two decades has been characterized by sluggish poverty reduction occurring alongside robust economic growth. Applying polarization measures to comparable survey data from 24 SSA countries, we find that there has been a generalizable increase in polarization over the past two decades—and in particular, an increased concentration of households in the lower tail of the welfare distribution of SSA countries. The polarization process is further analyzed by identifying the main drivers and singling out the effect of different covariates at different points in the consumption distribution. This investigation reveals that the drivers of polarization are relatively similar across SSA: demographic, urban/rural, regional variables and access to basic infrastructure are found to be the most important drivers of polarization in many countries.","PeriodicalId":51524,"journal":{"name":"Journal of African Economies","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1093/JAE/EJAB006","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44632641","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"经济学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper explores the relationship between tax rates and tax evasion in a low-income country context: Ethiopia. By using transaction-level administrative trade data, we are able to provide an analysis that is largely comparable with the rest of the literature while also introducing two important innovations. First, we compare the elasticity of evasion to statutory tax rates and effective tax rates (ETRs). Most studies in the literature so far focused on the former. We show that ETRs are the most relevant parameter to explain evasion in contexts where exemptions are widespread, which results in a large divergence between ETRs and the statutory rates set out in the law. Second, we account for trade costs more precisely than the previous literature by adjusting the trade gap rather than controlling for proxies. We argue that this new approach to accounting for trade costs is superior to those previously adopted in the literature.
{"title":"Trade Tax Evasion and the Tax Rate: Evidence from Transaction-level Trade Data","authors":"A. Mengistu, K. G. Molla, G. Mascagni","doi":"10.1093/JAE/EJAB005","DOIUrl":"https://doi.org/10.1093/JAE/EJAB005","url":null,"abstract":"\u0000 This paper explores the relationship between tax rates and tax evasion in a low-income country context: Ethiopia. By using transaction-level administrative trade data, we are able to provide an analysis that is largely comparable with the rest of the literature while also introducing two important innovations. First, we compare the elasticity of evasion to statutory tax rates and effective tax rates (ETRs). Most studies in the literature so far focused on the former. We show that ETRs are the most relevant parameter to explain evasion in contexts where exemptions are widespread, which results in a large divergence between ETRs and the statutory rates set out in the law. Second, we account for trade costs more precisely than the previous literature by adjusting the trade gap rather than controlling for proxies. We argue that this new approach to accounting for trade costs is superior to those previously adopted in the literature.","PeriodicalId":51524,"journal":{"name":"Journal of African Economies","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1093/JAE/EJAB005","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41431122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"经济学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Despite the past centuries' economic setbacks and challenges, are there reasons for optimism about Africa's economic prospects? We provide a conceptual framework and empirical evidence that show how the nature of African society has led to three sets of unrecognised ‘latent assets.’ First, success in African society is talent driven and Africa has experienced high levels of perceived and actual social mobility. A society where talented individuals rise to the top and optimism prevails is an excellent basis for entrepreneurship and innovation. Second, Africans, like westerners who built the world's most successful effective states, are highly sceptical of authority and attuned to the abuse of power. We argue that these attitudes can be a critical basis for building better institutions. Third, Africa is ‘cosmopolitan.’ Africans are the most multilingual people in the world, have high levels of religious tolerance and are welcoming to strangers. The experience of navigating cultural and linguistic diversity sets Africans up for success in a globalised world.
{"title":"Africa's Latent Assets","authors":"Soeren J. Henn, James A. Robinson","doi":"10.3386/W28603","DOIUrl":"https://doi.org/10.3386/W28603","url":null,"abstract":"\u0000 Despite the past centuries' economic setbacks and challenges, are there reasons for optimism about Africa's economic prospects? We provide a conceptual framework and empirical evidence that show how the nature of African society has led to three sets of unrecognised ‘latent assets.’ First, success in African society is talent driven and Africa has experienced high levels of perceived and actual social mobility. A society where talented individuals rise to the top and optimism prevails is an excellent basis for entrepreneurship and innovation. Second, Africans, like westerners who built the world's most successful effective states, are highly sceptical of authority and attuned to the abuse of power. We argue that these attitudes can be a critical basis for building better institutions. Third, Africa is ‘cosmopolitan.’ Africans are the most multilingual people in the world, have high levels of religious tolerance and are welcoming to strangers. The experience of navigating cultural and linguistic diversity sets Africans up for success in a globalised world.","PeriodicalId":51524,"journal":{"name":"Journal of African Economies","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45800800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"经济学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
John P. Dougherty, Richard A. Gallenstein, K. Mishra
Recent research suggests that coupling microfinance loans with an index insurance policy may be a cost-effective way to expand credit market access to smallholder farmers in developing countries. Index insurance can increase demand for credit and encourage increased supply of credit by protecting borrowers and lenders from covariate production shocks that discourage credit market expansion. In this paper, we propose that index insurance, when bundled with credit, may also reduce a different barrier to credit market access: high transaction costs caused by moral hazard in the credit market. We develop a theoretical model of a competitive credit market with moral hazard. In this market, lenders use either dynamic incentives or collateral to mitigate the moral hazard problem. The model shows that index insurance bundled with loan contracts can reduce moral hazard and increase borrower welfare. We then test the model and find some empirical support using a subset of data from a randomised control trial in northern Ghana.
{"title":"Impact of Index Insurance on Moral Hazard in the Agricultural Credit Market: Theory and Evidence from Ghana","authors":"John P. Dougherty, Richard A. Gallenstein, K. Mishra","doi":"10.1093/JAFECO/EJAB003","DOIUrl":"https://doi.org/10.1093/JAFECO/EJAB003","url":null,"abstract":"\u0000 Recent research suggests that coupling microfinance loans with an index insurance policy may be a cost-effective way to expand credit market access to smallholder farmers in developing countries. Index insurance can increase demand for credit and encourage increased supply of credit by protecting borrowers and lenders from covariate production shocks that discourage credit market expansion. In this paper, we propose that index insurance, when bundled with credit, may also reduce a different barrier to credit market access: high transaction costs caused by moral hazard in the credit market. We develop a theoretical model of a competitive credit market with moral hazard. In this market, lenders use either dynamic incentives or collateral to mitigate the moral hazard problem. The model shows that index insurance bundled with loan contracts can reduce moral hazard and increase borrower welfare. We then test the model and find some empirical support using a subset of data from a randomised control trial in northern Ghana.","PeriodicalId":51524,"journal":{"name":"Journal of African Economies","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1093/JAFECO/EJAB003","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47288028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"经济学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Traders in informal grain markets often lack incentives to sell grain dried to a moisture level that is safe for storage, due to weak regulations and lack of low-cost moisture testing technologies. This study estimated the demand for a third-party moisture testing service in western Kenya that can encourage safe drying and reduce asymmetric information between buyers and sellers. We utilised a Becker–DeGroot–Marschak (BDM) auction to obtain maize traders’ willingness to pay (WTP) for the moisture testing service and compared it with two alternative multiple price list (MPL) mechanisms for eliciting WTP. Traders had the opportunity to bid on the testing service with two different moisture metres. The first was a low-cost hygrometer that measures temperature and relative humidity and costs about $2.50. The second was a commercial moisture metre that costs $170 in USA but provides a more precise reading. Results suggest that the standard BDM auction and both MPL variants produced similar estimates of demand for our moisture testing service. On average, traders were willing to pay $0.28 to have their maize tested with the hygrometer and $0.39 with the moisture metre. An additional take-it-or-leave-it auction for the hygrometer itself revealed that traders were not sensitive to price changes around market price, although only 15% of the traders purchased the device. A service provider model using either device could be a way to make moisture testing accessible in rural grain markets in the absence of a supply chain that sells these devices directly.
{"title":"Estimating Demand for Third-party Quality Testing in Rural Grain Markets: Evidence from an Experimental Auction for Measuring Moisture Content in Kenya","authors":"A. Fuller, Jacob Ricker-Gilbert","doi":"10.1093/JAE/EJAB002","DOIUrl":"https://doi.org/10.1093/JAE/EJAB002","url":null,"abstract":"\u0000 Traders in informal grain markets often lack incentives to sell grain dried to a moisture level that is safe for storage, due to weak regulations and lack of low-cost moisture testing technologies. This study estimated the demand for a third-party moisture testing service in western Kenya that can encourage safe drying and reduce asymmetric information between buyers and sellers. We utilised a Becker–DeGroot–Marschak (BDM) auction to obtain maize traders’ willingness to pay (WTP) for the moisture testing service and compared it with two alternative multiple price list (MPL) mechanisms for eliciting WTP. Traders had the opportunity to bid on the testing service with two different moisture metres. The first was a low-cost hygrometer that measures temperature and relative humidity and costs about $2.50. The second was a commercial moisture metre that costs $170 in USA but provides a more precise reading. Results suggest that the standard BDM auction and both MPL variants produced similar estimates of demand for our moisture testing service. On average, traders were willing to pay $0.28 to have their maize tested with the hygrometer and $0.39 with the moisture metre. An additional take-it-or-leave-it auction for the hygrometer itself revealed that traders were not sensitive to price changes around market price, although only 15% of the traders purchased the device. A service provider model using either device could be a way to make moisture testing accessible in rural grain markets in the absence of a supply chain that sells these devices directly.","PeriodicalId":51524,"journal":{"name":"Journal of African Economies","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44286622","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"经济学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We analyze the domestic transport and logistics costs of importing a 20-foot container into Africa. We run regressions on a panel of 50 African countries for the period 2006–2014 using the RE-2SLS estimator. Distance from port of arrival to the point of delivery is an important explanatory factor of cost. Time-varying variables yield additional and valuable information. Reducing processing times and adjusting the ratio of the purchasing power parity conversion factor to the market exchange rate would contribute to save on the cost to import.
{"title":"What Factors Drive Transport and Logistics Costs in Africa?","authors":"P. Plane","doi":"10.1093/JAE/EJAA019","DOIUrl":"https://doi.org/10.1093/JAE/EJAA019","url":null,"abstract":"\u0000 We analyze the domestic transport and logistics costs of importing a 20-foot container into Africa. We run regressions on a panel of 50 African countries for the period 2006–2014 using the RE-2SLS estimator. Distance from port of arrival to the point of delivery is an important explanatory factor of cost. Time-varying variables yield additional and valuable information. Reducing processing times and adjusting the ratio of the purchasing power parity conversion factor to the market exchange rate would contribute to save on the cost to import.","PeriodicalId":51524,"journal":{"name":"Journal of African Economies","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2021-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45780305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"经济学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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