The Effect Of The Second Child On The Cognitive Skill Outcomes Of The First Child Based On CFPS Data

According to the " Quantity-Quality Tradeoff " model of children,the increase of the number of children in a family will make the quality of children decline.Based on the data from the China Family Panel Studies(CFPS),this paper studies whether the birth of the second child has a significant negative impact of the first child in the family on the cognitive skill,including Chinese,math and comprehensive cognitive abilities.In addition to OLS regression,this paper also uses the relaxation of onechild-policy in China and the results about the relaxation of One-Child Policy in the CFPS community questionnaire survey data,as the two separate instrumental variable of family size,this paper uses two-stage least square method(2SLS)to analyze the effect of the second child on the cognitive skill outcomes of the first child.When the relaxation of One-Child Policy is used as an instrumental variable,including the provincial level selective two-child policy,universal two-child policy,based on the panel data of five years of CFPS,the fixed effect model is adopted,and other variables are controlled,both OLS and 2SLS regression results showed that the second birth had no significant negative impact on the math,Chinese and cognitive performance of the first child.When the universal two-child policy is taken as the instrumental variable,the instrumental variable fails.When the selective two-child policy is adopted as the instrumental variable,although the selective two-child policy has a significant positive effect on the second child birth,the F statistic value is still small,and it is not a particularly good instrumental variable.When the results about the relaxation of one-child-policy in the CFPS community questionnaire survey data were selected as the instrumental variable of family size change,and use the crosssection data of two years,after controlling other variables and the fixed effect of time.The OLS results showed that the second child birth had a significant negative impact on the math,Chinese and cognitive scores of the first child.However,the results of2 SLS regression showed that second child birth had no significant negative impact on the overall achievement of math,Chinese and cognitive ability of the first child.The results of this paper show that in OLS,the negative impact of the second child on the first child is more likely to come from the selective bias,that is,the negative impact may come from the difference in the background of the two-child family and the only child family,while the birth of the second child itself does not have a significant negative impact on the cognitive ability of the first child.The results of this study also show that the parents’ education level in the family plays an important role in improving the cognitive ability of the firstborn.Based on the research results,this paper provides some suggestions for parents’ reproductive decision-making and national fertility policy,and puts forward the research limitations and future prospects.