Impact of Urbanization on Cropping Structure: Empirical Evidence from China
Round 1
Reviewer 1 Report
The article is devoted to an urgent problem for China. The article contains an overview of modern literature relevant to the chosen topic. The novelty of the study is very poorly justified, since the actual models cannot be the basis of novelty. The authors need to substantiate the contribution of this research to the scientific discourse. For example, you can select the Discussion section separately. Not all the results are justified in the main part of the article. For example, the contribution of the territorial structure of the workforce has not been verified in the simulation. In addition, the authors discuss the effects of labor mobility, employment structures. These effects were also not recorded in the models. It is recommended either to refine the models or to more clearly record the contribution of this study.
Author Response
Dear reviewer,
Thank you so much for your comments, we have revised manuscript following the suggestions. Comments are in black font, and red is the answers. For any modification that is not correct, please give your further comments. Thank you again.
Comments: The article is devoted to an urgent problem for China. The article contains an overview of modern literature relevant to the chosen topic.
The novelty of the study is very poorly justified, since the actual models cannot be the basis of novelty. The authors need to substantiate the contribution of this research to the scientific discourse. For example, you can select the Discussion section separately.
Not all the results are justified in the main part of the article. For example, the contribution of the territorial structure of the workforce has not been verified in the simulation. In addition, the authors discuss the effects of labor mobility, employment structures. These effects were also not recorded in the models. It is recommended either to refine the models or to more clearly record the contribution of this study.
ANSWER：The revised manuscript adds a section on "7. Discussion" and focuses on the possible innovative and marginal contributions of the article while explaining the research shortcomings. The details are as follows:
Food security is a matter of national and regional social stability. This article exam-ines the issue of cropping restructuring, which is directly related to food security, focusing on an empirical analysis of the impact of migration in rural regions on cropping restructuring based on provincial panel data in China. The main innovations of this paper are as follows. Firstly, it confirms the potential threshold characteristics of urbanization affecting cropping structure adjustment, namely under the labor supply constraint, adjusting planting structure is only a phase behavior. Secondly, it analyzes the potential heterogeneity of urbanization affecting cropping structure adjustment in Main Grain-Producing Regions, Main Grain-Selling Regions, and Balanced Production and Marketing Regions, which provides a theoretical basis for formulating and implementing differentiated policies. Thirdly, it explores the effect of labor migration distance in rural on cropping structure adjustment, which can provide theoretical support for differentiated urbanization strategies.
However, there are still some shortcomings in this paper for future research to continue to improve. This study explores the stage characteristics of cropping restructuring under the labor supply constraint but does not explore the new production strategy and their impact on food security after the labor supply constraint is further tightened after urbanization crosses the threshold. Future research can continue to explore the dynamic changes in production behavior according to the logic of labor supply constraints and collect relevant data for further empirical analysis.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The paper is well-structured, empirical analysis is extensive, well-substantiated, and thorough. The use of different models provides a solid framework to support inferences. However, please consider the following suggestions:
- Please provide more descriptive elements for context; giving more information about the regions considered and their peculiarities would be important. This element of different regions is addressed in the paper, indeed, however, perhaps the aggregation into two/three large groupings does not capture some important aspects that differentiate the 31 regions.
- The discussion should be more nourished, with more references to other studies’ results on the same topic or on different topics but that have applied the same statistical methodologies. This could lend more support to the choices made with respect to the models used.
- With regard to policy, it would be important to highlight some recommendation that should be declined based not only on the differences that emerged from the results of the quantitative analysis performed, but also on the basis of qualitative elements derived from guidelines or policy documents, which should then be referred to and included in the References section.
Author Response
Dear reviewer,
Thank you so much for your comments, we have revised manuscript following the suggestions. Comments are in black font, and red is the answers. For any modification that is not correct, please give your further comments. Thank you again.
Comments: The paper is well-structured, empirical analysis is extensive, well-substantiated, and thorough. The use of different models provides a solid framework to support inferences. However, please consider the following suggestions:
- Please provide more descriptive elements for context; giving more information about the regions considered and their peculiarities would be important. This element of different regions is addressed in the paper, indeed, however, perhaps the aggregation into two/three large groupings does not capture some important aspects that differentiate the 31 regions.
ANSWER：Background information on China's functional grain regions has been added to the revised version:
“In order to leverage regional comparative advantages and ensure food security, China 31 province were divided into Main Grain-Producing Regions with 13 provinces, Main Grain-Selling Regions with 7 provinces and Balanced Production and Marketing Regions with 11 provinces since the 1990s. The main grain-producing regions are suitable for growing food crops in terms of geography, soil, climate as well as other natural conditions, with high grain yield and a large proportion of cultivation to ensure self-sufficiency while also being able to transfer out as commodity grain. In 2022, the main grain-producing reions including Heilongjiang, Jilin, Liaoning, Inner Mongolia, Hebei, Henan, Shandong, Jiangsu, Anhui, Jiangxi, Hubei, Hunan and Sichuan account for more than 78% of total grain production, bearing a major responsibility to ensure national food security. The main grain-selling regions are relatively economically developed, but with more people and less land, there is a large gap between grain production and demand, including Beijing, Tianjin, Shanghai, Zhejiang, Fujian, Guangdong and Hainan. The balanced production and marketing regions make limited contribution to the national grain production but can basically maintain self-sufficiency, including Shanxi, Ningxia, Qinghai, Gansu, Tibet, Yunnan, Guizhou, Chongqing, Guangxi, Shaanxi and Xinjiang.”
It should be noted that when we explore heterogeneity, China 31 provinces were divided into main grain-producing regions with 13 provinces, main grain-selling regions with 7 provinces, and balanced production and marketing regions with 11 provinces. The main consideration is that this paper focuses on the issue of cultivated land cropping structure, which is directly related to food security, and the target remains to guarantee food security through policy design and adjustment. Each functional grain region is assigned different roles in guaranteeing food security, and according to the findings of the study, it is significant to develop and implement differentiated policies to guarantee food security. In addition, limited by the data available at the provincial level, further subdivision of the sample may lead to a reduction in the sample size of the subgroups, which may adversely affect the results. In later studies, the sample could be further refined for in-depth study after obtaining data at the county or city levels.
- The discussion should be more nourished, with more references to other studies’ results on the same topic or on different topics but that have applied the same statistical methodologies. This could lend more support to the choices made with respect to the models used.
ANSWER：The section of the revised manuscript, "4.1 Benchmark results" adds a comparison and discussion of the results with existing relevant studies, in particular, a comparison of the results of empirical studies using different methods and samples to support the conclusions of this article.
- With regard to policy, it would be important to highlight some recommendation that should be declined based not only on the differences that emerged from the results of the quantitative analysis performed, but also on the basis of qualitative elements derived from guidelines or policy documents, which should then be referred to and included in the References section.
ANSWER：A policy recommendation was added in revised manuscript: “Fourth, to support the county as an important carrier of urbanization, from urban construction as the center of gravity to rural construction as the center, to achieve local employment, to improve the flexibility and effectiveness of factor inputs, to meet the employment process of farmers to settle and return to their hometown employment and entrepreneurship needs.”
The main consideration for such a revision is that in 2022, China implemented the Opinions on Promoting Urbanization with Counties as Important Carriers, which proposed the development of people-centered county urbanization, and the findings of this paper support the reliability of the policy to a certain extent and provide support for local employment in the vicinity.
Author Response File: Author Response.docx
Reviewer 3 Report
About the submission with the title "Impact of Urbanization on Cropping Structure: Empirical Evidence from China" I have the following comments:
The abstract must be clear about main motivations, gaps that justify the research, objectives, methodologies, novelties and main insights. This must be presented deeply in the introduction section. For example, what is the meaning of the following sentence : "When urbanization is lower than the threshold value of 81.55%, it plays a promoting role in the adjustment of agricultural planting structure towards grain, but it’s not sig-nificant after crossing the threshold limitation.".
The literature review is weak and must be improved. Considering 38 references for a scientific document seems few, namely when a section for the literature review is presented.
The methods proposed need better scientific support and must be compared with other approaches, because I have some doubts if the Trobit methodologies is the more appropriate for the panel data. The selection of the variables needs also better explanation and scientific support.
My main concerns are about the results for the regressions and the complete absence of information about potential problems related to, for example, multicollinearity, heteroscedasticity, endogeneity, normality, autocorrelation (time seiries and spatial), linearity, etc.
A discussion section is missing and the conclusions section must focus on main insights obtained with the research, policy recommendation, practical implications and future research.
Author Response
Dear reviewer,
Thank you so much for your comments, we have revised manuscript following the suggestions. Comments are in black font, and red is the answers. For any modification that is not correct, please give your further comments. Thank you again.
About the submission with the title "Impact of Urbanization on Cropping Structure: Empirical Evidence from China" I have the following comments:
The abstract must be clear about main motivations, gaps that justify the research, objectives, methodologies, novelties and main insights. This must be presented deeply in the introduction section. For example, what is the meaning of the following sentence: "When urbanization is lower than the threshold value of 81.55%, it plays a promoting role in the adjustment of agricultural planting structure towards grain, but it’s not significant after crossing the threshold limitation.".
ANSWER：The abstract was revised thoroughly, some important elements, for example, motivation, objectives, methodology, and innovation was all interpreted. The abstract revised as follows:
Food security is a national priority and a cornerstone for maintaining national and regional stability. Focusing on cropping structure directly related to food security, this paper estimates the causal effect of urbanization on cropping restructuring in China. We use provincial panel data between 2000 and 2019 and threshold regression models to identify potential structural mutation characteristics. The study is an attempt to fill the cognitive gap for nonlinear relationship be-tween urbanization and cropping restructure. Urbanization forms agricultural labor supply constraints that significantly increased the share of sown area of grain crops, but with obvious threshold characteristics, and the effect of urbanization on cropping structure was no longer significant after crossing the threshold. Urbanization in the main grain-producing regions and main grain-selling regions promoted the adjustment of cropping structure in the direction of grain, but was not significant in balanced production and marketing regions. Short-distance urbanization did not bring significant effects on cropping restructuring. We propose several suggestions for cultivated land planting structure, urbanization, and food security.
The literature review is weak and must be improved. Considering 38 references for a scientific document seems few, namely when a section for the literature review is presented.
ANSWER：We have made further additions to the literature review section, as well as in the discussion of variables, models, and empirical results section. The current number of references is 61.
The methods proposed need better scientific support and must be compared with other approaches, because I have some doubts if the Trobit methodologies is the more appropriate for the panel data. The selection of the variables needs also better explanation and scientific support.
ANSWER: Based on the reviewer's suggestion, we introduce some authoritative literature in the model setting section. In fact, the Tobit model for panel data has been applied in many literatures and is often used to deal with censored data. However, it should be noted that the main empirical method in this paper is still the FE, and the Tobit model is only used as a robustness check, mainly to play an auxiliary validation role.
My main concerns are about the results for the regressions and the complete absence of information about potential problems related to, for example, multicollinearity, heteroscedasticity, endogeneity, normality, autocorrelation (time seiries and spatial), linearity, etc.
ANSWER: The issues raised by the reviewers are important. Potential problems, for example, multicollinearity, heteroskedasticity, endogeneity, and autocorrelation may exist in the model, but multicollinearity, heteroskedasticity, as well as autocorrelation affect the significance of the coefficients and will not impact the unbiasedness and consistency of the parameter estimates, and to some extent the use of fixed effects and robust standard errors can significantly improve the robustness of the results, so the article does not address the relevant issues. However, the most critical issue is the endogeneity, because the endogeneity problem can lead to biased and inconsistent parameter estimates. In this paper, we deal with the potential endogeneity and introduce IV for 2SLS estimation. Of course, finding a more appropriate IV may be an important task in later related studies.
A discussion section is missing and the conclusions section must focus on main insights obtained with the research, policy recommendation, practical implications and future research.
ANSWER：The "7. Discussion" was added as a separate section in the revised manuscript, and focuses on the possible innovative and marginal contributions of the article while explaining the research shortcomings. The details are as follows:
Food security is a matter of national and regional social stability. This article examines the issue of cropping restructuring, which is directly related to food security, focusing on an empirical analysis of the impact of migration in rural regions on cropping restructuring based on provincial panel data in China. The main innovations of this paper are as follows. Firstly, it confirms the potential threshold characteristics of urbanization affecting cropping structure adjustment, namely under the labor supply constraint, adjusting planting structure is only a phase behavior. Secondly, it analyzes the potential heterogeneity of urbanization affecting cropping structure adjustment in Main Grain-Producing Regions, Main Grain-Selling Regions, and Balanced Production and Marketing Regions, which provides a theoretical basis for formulating and implementing differentiated policies. Thirdly, it explores the effect of labor migration distance in rural on cropping structure adjustment, which can provide theoretical support for differentiated urbanization strategies.
However, there are still some shortcomings in this paper for future research to continue to improve. This study explores the stage characteristics of cropping restructuring under the labor supply constraint but does not explore the new production strategy and their impact on food security after the labor supply constraint is further tightened after urbanization crosses the threshold. Future research can continue to explore the dynamic changes in production behavior according to the logic of labor supply constraints and collect relevant data for further empirical analysis.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
All comments were taken into account by the authors.
Author Response
Dear reviewer,
We are grateful for your comments. Authors all believe the quality of the article was improved greatly under your suggestions. Thank you again.
Comments1: All comments were taken into account by the authors.
Reviewer 3 Report
I suggest that the authors better address the following questions presented in my first report, because some of the answers are not correct:
"My main concerns are about the results for the regressions and the complete absence of information about potential problems related to, for example, multicollinearity, heteroscedasticity, endogeneity, normality, autocorrelation (time seiries and spatial), linearity, etc."
Author Response
Dear reviewer,
We are grateful again for your comments, we have revised manuscript following your suggestions. Comments are in black font, and red is the answers. For any modification that is not correct, please give your further comments. Thank you so much.
Comments3: I suggest that the authors better address the following questions presented in my first report, because some of the answers are not correct:
"My main concerns are about the results for the regressions and the complete absence of information about potential problems related to, for example, multicollinearity, heteroscedasticity, endogeneity, normality, autocorrelation (time seiries and spatial), linearity, etc."
ANSWERS: Following reviewer’s comments, several relevant issues, for example, multicollinearity, heteroscedasticity, normality, autocorrelation (time seiries and spatial), linearity were checked, and added into “4.1. Data check” section in the revised manuscript. Details as follows:
In this article, we check the heteroskedasticity with modified Wald test, which corresponds to a p-value of 0.000, indicating the existence of heteroskedasticity. Wooldridge test and Pesaran's test were used to check autocorrelation in time series as well as in spatial, and their corresponding p-value is 0.000 and 0.117, respectively. The results indicate the existence of time series autocorrelation, but cross-sectional autocorrelation was not supported. To overcome the problems of heteroskedasticity and within-group autocorrelation, this paper uses robust standard errors for clustering at the provincial level and reports the corresponding t-values. In addition, we added a multicollinearity check, and the VIF of each variable was less than 5 (VIF＜10 in general), indicating that there is no serious multicollinearity problem with the selected variables. We also check normality based on the Shapiro-Wilk test. The estimation results show that the p-value corresponding to each variable is greater than 0.05, and the null hypothesis that the data distributed normally cannot be rejected, indicating that the data distribution follows normality. Meanwhile, by plotting the scatter plots of the dependent variable and the urbanization this paper is interested, we find that they have a strong linear relationship, with only some divergence in distribution as the independent variables increase. But the linear relationship is satisfied overall.
Author Response File: Author Response.docx
