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The Impact of Attrition on the Children of the NLSY79 Alison Aughinbaugh a b s t r a c t This paper examines the impact of attrition among the women of the Na- tional Longitudinal Survey of Youth 1979 NLSY79 and children in the NLSY79 Mother-Child Supplement NLSY79-C. Attrition among the chil- dren is nonrandom with respect to mother’s marital status, grandfather’ s completed schooling, and family income. These differences that are re- lated to the probability of attrition do not appear to impact estimates of the effects of family income or maternal employment early in the child’s life on either PPVT or BPI standard scores. However, the women who are not interviewed in any child-supplement year and the children for whom supplemental information is never collected appear to be the most disadvantaged. The omission of these children from the NLSY79-C may impact estimates of family characteristics on child outcomes, but because there are relatively few such children, the effects of their omission are likely to be small.

I. Introduction

The National Longitudinal Survey of Youth 1979 NLSY79 and its corresponding Mother-Child Supplement NLSY79-C are widely used to study the outcomes of children and the impact that children have on women’s economic and demographic decisions. As the children of the NLSY79-C age, these data can be used to study important intergenerational relationships regarding human capital Alison Aughinbaugh is a research economist at the U.S. Bureau of Labor Statistics. The views ex- pressed are those of the author and do not reect the policies of the Bureau of Labor Statistics or the views other BLS staff members. The author thanks Tom Mroz, Mike Horrigan, Frank Mott, Chuck Pierret, Donna Rothstein, and anonymous referees for useful comments. The author takes responsibility for all errors. The data used in this article can be obtained beginning October 2004 through Septem- ber 2007] from Alison Aughinbaugh, 2 Massachusetts Ave. NE, Room 4945, Washington, DC 20212, aughinbaugh.alisonbls.gov. [Submitted July 1999; accepted July 2003] ISSN 022-166X; E-ISSN 1548-8004 Ó 2004 by the Board of Regents of the University of Wisconsin System T H E J O U R N A L O F H U M A N R E S O U R C E S • X X X I X • 2 investment and the impact of family background on child outcomes. However, non- random attrition may impact the data set’s ability to examine such questions. The NLSY79 began in 1979 as a nationally representative sample of young men and women between the ages of 14 and 21 on December 31, 1978. Detailed annual information on fertility, marital transitions, employment, and income is available in this data set. Biennially, beginning in 1986, the mothers among the NLSY79 partici- pants were asked detailed questions about their children, and the children were given a battery of cognitive and behavioral assessments. It is this information that makes up the NLSY79-C. Because the NLSY79-C is made up of the children of the female respondents in the NLSY79, it is designed to be representative of the NLSY79 wom- en’s fertility up to the year of the last survey. By design, the NLSY79-C is not repre- sentative of a cross-section of children. Moreover, it is not representative of all chil- dren born to women in the NLSY79 cohort because their fertility is not yet complete. 1 In this study, I examine the effects of attrition on the NLSY79-C using methods employed by MaCurdy, Mroz, and Gritz 1998 and Fitzgerald, Gottschalk, and Mof- Žtt 1998 to study the effects of attrition on the NLSY79 and the Panel Study of Income Dynamics PSID, respectively. The results in this paper show that over the years that the NLSY79-C is collected attrition among the women and children has a relatively small effect on the family background measures, such as women’s marital status, fertility, and family income, and on estimates of two important intergenera- tional relationships: 1 the effect of family income on child development and 2 the effect of maternal employment in the child’s Žrst year on child development. Although only about 2 percent of the women in the NLSY79 attrite prior to 1986 and never return to the survey, the women who are not interviewed in 1986 or any later year are unlike those who are interviewed in at least one of the NLSY79-C years. The women who are not interviewed in any of the NLSY79-C years are more likely to have had an early birth or marriage. Additionally, the children for whom the supple- mental information was never collected tend to have mothers who experienced an early birth or marriage. Although attrition over the course of the NLSY79-C has little effect, attrition prior to the supplement’s beginning may have a larger impact. In most respects, for the measures of family background considered here, the picture drawn when all child observations are considered is no different than the picture drawn when only the nonattritors are examined. Future attrition from the NLSY79-C, however, is more likely for children whose families had higher incomes during their Žrst three years and less likely for those children whose mothers had never married by the interview in which the child was Žrst assessed and whose grandfathers had completed more schooling. Despite these systematic differences in the probability of attrition, relationships between either family income and early child assessment scores or maternal employment and assessment scores are largely unaffected by the omission of the attritors. This paper is organized as follows. In Section II, I present descriptive statistics to assess the patterns of attrition among women in the NLSY79 and the children in the NLSY79-C and to assess how the characteristics of the attritors impact family background, as measured by mother’s highest grade completed and family income, 1. The data through 1998 contain over 80 percent of the NLSY women’s completed fertility Baker et al. 2000. and the children’s scores on developmental assessments. This is done by comparing the full sample with the sample of respondents who have never missed an interview. Section III examines how attrition affects estimates of the relationship between fam- ily characteristics and the children’s assessment scores. Lastly, Section IV summa- rizes and discusses the Žndings.

II. Attrition Patterns