Yuyu Chen is an associate professor at the Department of Applied Economics, Guanghua School of Management, Peking University, China. Hongbin Li is C.V. Starr Professor of Economics at the School
of Economics and Management, Tsinghua University, China. Lingsheng Meng is an assistant professor of economics at the School of Economics and Management, Tsinghua University, China. Chen thanks the
National Science Foundation of China Project No. 71073002 and No. 70903003 for fi nancial support. Li thanks the National Science Foundation of China Project No. 71025004 and No. 71121001 for fi nancial
support. The authors wish to thank Avi Ebenstein, Lena Edlund, Mark Duggan, Raymond Guiteras, John Ham, Melissa Kearney, Jeanne Lafortune, Soohyung Lee, Peter Murrell, Xiaobo Zhang, three anonymous
referees, and seminar participants at the University of Maryland, the CES Nanning Conference, and Hong Kong University of Science and Technology for helpful comments. The corresponding author is Lingsheng
Meng, Department of Economics, School of Economics and Management, Tsinghua University, Beijing 100084, China e- mail: menglshsem.tsinghua.edu.cn. The data used in this article can be obtained
beginning July 2013 through June 2016 from the corresponding author. [Submitted February 2011; accepted March 2012]
SSN 022 166X E ISSN 1548 8004 8 2013 2 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 • 48 • 1
Prenatal Sex Selection and Missing Girls in China
Evidence from the Diffusion of Diagnostic Ultrasound
Yuyu Chen Hongbin Li
Lingsheng Meng
A B S T R A C T
How much of the increase in sex ratio male to female at birth since the early 1980s in China is attributed to increased prenatal sex selection? This
question is addressed by exploiting the differential introduction of diagnostic ultrasound in the country during the 1980s, which signifi cantly reduced
the cost of prenatal sex selection. We fi nd that the improved local access to ultrasound technology has resulted in a substantial increase in sex ratio at
birth. Our estimates indicate that roughly 40 to 50 percent of the increase in sex imbalance at birth can be explained by local access to ultrasound
examinations.
I. Introduction
The population of China is characterized by a signifi cant sex imbal- ance that favors males Coale 1991. As reported in censuses, sex ratio defi ned as the
number of males per 100 females at birth rose from 108.5 in 1982 to 116.9 in 2000. The issue of “missing women” has attracted considerable interest from researchers and
policymakers since the seminal works of Sen 1990, 1992 suggested that substantial excess female mortality arising from sex discrimination was responsible for the huge
discrepancy. More importantly, the biased sex ratio may have been caused by sex- selective abortion—a procedure that has become possible thanks to modern science
Banister 2004; Chu 2001; Miller 2001. However, no previous study has shown large- sample evidence of the link between sex- selective abortion and sex imbalance.
1
This paper aims to provide empirical evidence that sex- selective abortion, an inad- vertent consequence of the introduction of diagnostic ultrasound in China, is a major
determinant of sex imbalance in the country. B- scan ultrasonography has become a highly controversial medical technology since its adoption in China. Although initially
introduced to improve diagnostic accuracy, it has been widely used to determine fetal sex since the 1980s, rendering sex- selective abortion possible. The biased sex ratio
not only has profound ethical implications for women’s welfare Croll 2000, but also causes adverse social consequences, such as a disturbed marriage market and rising
crime rates Ebenstein and Jennings 2009; Edlund et al. 2007. Although previous studies have examined the fi nancial costs of technological advances in medical care
for example, Newhouse 1992; Cutler and McClellan 2001; Cutler 2007, this paper demonstrates how the adoption of a new technology can contribute to a phenomenon
that has caused the concern for many policymakers and become a subject of much academic research.
In this paper, we construct a unique data set that tracks the differential diffusion of diagnostic ultrasound in China, which has created variation in access to prenatal sex
determination technology that may be orthogonal to demand factors. The data are ob- tained from numerous issues of the Local Chronicle, which provides a record of Chi-
nese local history, to identify the year in which ultrasound machines were introduced in approximately 1,500 Chinese counties. Subsequently, this data set was matched
with a large micro data set that contains the records of more than 500,000 live births in China from 1975 to 1992, a period of rapid expansion in ultrasound technology access.
The birth records in the micro data allow for the accurate measurement of sex ratio at birth
necessary for the analysis of prenatal sex selection. To estimate the effect of access to selective abortion on the sex ratio at birth, the
study employs a difference- in- differences DD approach that exploits the variation in the timing of ultrasound technology adoption across counties. During the study period,
induced abortion was legal and abortion services were offered in public health facili- ties throughout China, in the same manner as other medical procedures. Therefore,
access to sex- selective abortion depended crucially on the availability of ultrasound equipment capable of prenatal sex determination. Women who became pregnant after
the introduction of ultrasound technology were more likely to have knowledge of fetal sex than those who became pregnant prior to its introduction. Therefore, it is possible
to estimate the effects of better access to sex- selective abortion by comparing changes in the sex ratio at birth in counties that had adopted ultrasound technology relative to
those that had not.
1. Lin and Luoh 2008 investigate the biological causes of sex imbalance and fi nd only a very small effect of maternal hepatitis- carrier status on the sex ratio in Taiwan.
We fi nd that the adoption of ultrasound technology had a signifi cant effect on the sex ratio at birth in China. The estimates from our preferred specifi cation imply that
on average, introduction of ultrasound technology in a county increased the prob- ability of a male birth by 1.3 and 2.4 percentage points for second- order and third- or
higher- order births, respectively. If no sons had been born previously, having local access to ultrasound technology raised the probability of having a male child by 4.8
percentage points for second births, and 6.8 percentage points for third births. These fi ndings indicate that roughly 40 to 50 percent of the increase in sex imbalance at birth
during the 1980s can be explained by the local access to ultrasound technology.
2
These fi ndings are interpreted as clear evidence of prenatal sex selection in China during the
period under consideration. A number of robustness checks support the key identifying assumption that the
timing of ultrasound technology introduction is uncorrelated with differential trends in sex ratios. First, the timing of the introduction does not pick up the effect of the One
Child Policy, an important contributing factor to the high sex ratio in China Ebenstein 2010; Edlund et al. 2007.
3
Furthermore, ultrasound technology affected only those who were subject to the One Child Policy, suggesting an interacting effect of the two
variables. Second, we show in a number of ways that our basic results are unlikely to be driven by spurious trends. Specifi cally, an event- study analysis confi rms that
there were no preexisting differential trends in sex ratio at birth in counties with and without access to ultrasound technology, and that the increase in the proportion of
males among high- order births was closely linked to the introduction of ultrasound technology.
This study contributes to our understanding of the instrument for achieving the ob- served sex imbalance in China. In existing empirical analyses based on large samples,
a general attempt is made to implicate sex- selective abortion in China indirectly, by virtue of fi ndings such as the rising differential in the sex ratio with birth order and the
female ratio of older siblings Zeng et al. 1993; Das Gupta 2005; Ebenstein 2010.
4
However, no previous research has presented direct large- sample evidence of sex- selective abortion or quantifi ed its effect on the sex ratio at birth in China.
5
The adoption of ultrasound removed the technological constraints on sex selection in China. Female infanticide is regarded more aversively than prenatal sex selection,
and the availability of prenatal sex determination allows those who otherwise would not have sex- selected to sex- select. Importantly, the new technology makes low- cost
prenatal sex determination possible at an earlier stage of gestation, and the process of technology diffusion is generally irreversible. As a result, we may expect persistently
high sex ratios in China and elsewhere.
The remainder of the paper is organized as follows. Section II provides a back- ground on the motivation for sex selection in China and how this selection may be
achieved through sex- selective abortion. Section III describes the empirical strategy.
2. Section V presents details of the calculation. 3. Enforcement of the policy is known to be highly localized and varying over time Greenhalgh 1986; Short
and Zhai 1998; Scharping 2003; Gu et al. 2007. 4. Almond and Edlund 2008 and Abrevaya 2009 observe a similar pattern of male- biased sex ratio among
U.S.- born children of Chinese, Korean, and Asian Indian parents. 5. In a related study, Lin, Liu, and Qian 2008 study the effect of sex- selective abortion in Taiwan and fi nd
that it increases the sex ratio, especially for higher- order births.
Section IV discusses the data and presents a number of descriptive statistics. Sec- tions V and VI report the empirical results and robustness tests. Finally, Section VII
concludes the paper.
II. Background
