Mate Availability and Women's Sexual Experiences in China

Adult sex ratios: causes of variation and implications for animal and human societies

Converging lines of inquiry from across the social and biological sciences target the adult sex ratio (ASR; the proportion of males in the adult population) as a fundamental population-level determinant of behavior. The ASR, which indicates the relative number of potential mates to competitors in a population, frames the selective arena for competition, mate choice, and social interactions. Here we review a growing literature, focusing on methodological developments that sharpen knowledge of the demographic variables underlying ASR variation, experiments that enhance understanding of the consequences of ASR imbalance across societies, and phylogenetic analyses that provide novel insights into social evolution. We additionally highlight areas where research advances are expected to make accelerating contributions across the social sciences, evolutionary biology, and biodiversity conservation.

Too Many Males or Too Many Females? Classroom Sex Ratio, Life History Strategies and Risk-Taking Behaviors

Prior research finds that sex ratio, defined as the proportion of males and females in a given context, is related to engagement in risk-taking behaviors. However, most research operationalizes sex ratio at a local context (e.g., regional or county), which fails to reflect with precision the sex ratios contexts of individuals at a closer level. Furthermore, the relationship between sex ratio and risk-taking behaviors may be affected by individuals’ life history strategy, with previous studies showing fast life history strategies linked to risk-taking behaviors, compared to slow life history strategies. The present study analyzes the relationship between classroom sex ratio and risk-taking behaviors and the interaction between classroom sex ratio and life history strategy in adolescents. The sample comprised 1214 participants nested in 57 classrooms, 49.75% females, 91.5% Spanish and a mean age of 16.15 years (SD = 1.23, range 14–21). Results from multilevel modeling showed a negative relation between classroom sex ratio and risk-taking behaviors in female adolescents with faster life history strategy. By contrast, classroom sex ratio in male adolescents related positively to risk-taking behaviors but did not interact with life history strategy. These findings underscore the importance of studying proximate sex ratio on risk-taking behaviors in adolescents and underline its potential influence in the development and expression of life history strategies.

Patterning of Sexual Violence against Women across US Cities and Counties

Sexual violence against women is a global public health concern; yet, determining its patterning is still largely understudied. An excess of males has emerged as a central concern given that men are the primary perpetrators of violent behavior, particularly against women. However, it is increasingly unclear as to whether an excess or, rather, a shortage of men drives purported negative social outcomes. To address these conflicting expectations, we target data from the U.S. Census and the National Incident-Based Reporting System to explore the patterning of sexual violence against women across cities and counties in the United States. Through the use of generalized linear mixed models, we assess the role of adult sex ratio imbalance, along with measures of gender inequality, on sexual violence. Our results indicate mixed support for competing predictions. Violence does not simply increase by way of male surplus or shortage, but instead with increasing skew in the sex ratio. That is, balanced sex ratios exhibit the lowest rates of violence. However, rates of sexual violence against women increase more quickly with increasing male scarcity and are lowest at low levels of male excess (51%). Thus, our findings are particularly challenging to interpret from a ‘more males = more violence’ framework because violence increases more quickly with female excess and is rarest with a slight male bias in the population. We argue that these results highlight a need to target the specific types of violent behaviors expected to be motivated by partner availability, rather than overly simplistic predictions of male surfeit or deficit leading to an excess of violence.

The Rise of Sonless Families in Asia and North Africa

A neglected consequence of declining fertility is the likely rise of families with children of one sex-only sons or only daughters. Increases in such families present important demographic shifts that may weaken patrilineal family systems. We assess whether sons-only and daughters-only families rose in Asia and North Africa from the early 1990s to around 2015. Using 88 surveys and two censuses, we examine how the number and sex composition of children of mothers aged 40-49 changed across 20 countries, representing 87% of the region's population and 54% of the global population. We also compare observed trends to sex-indifferent counterfactuals, quantify contributions of fertility declines with decompositions, and investigate subnational trends in China and India. Increases in sons-only families were universal where numbers of children fell. Growth of daughters-only families was suppressed in patrilineal contexts, but these sonless families still rose significantly in 13 of 18 countries where numbers declined. By 2015, over a quarter of families in the region had only sons and nearly a fifth only daughters. There was considerable variation across countries: recent levels ranged from 28.3% to 3.4% daughters-only and from 40.1% to 6.0% sons-only. China and the rest of East Asia had the highest shares.

The Impact of National-Level Gender Inequality on the Sexual Abuse of Girls

Feminist scholars from various social science disciplines posit that gender inequality (GI) is harmful to women's well-being. Feminist criminologists argue that GI is criminogenic, especially of sexual violence. I apply this framework to a specific form of sexual violence: child sexual abuse (CSA). Using multilevel generalized linear modeling to analyze the responses of 10,106 women from 27 countries in the International Dating Violence Study, I test for significant associations between national-level GI and self-reported retrospective reports of CSA. While controlling for other risk factors, I find that GI is significantly associated with increased odds of having experienced CSA among women.

Do Local Sex Ratios Approximate Subjective Partner Markets? : Evidence from the German Family Panel

Sex ratios have widely been recognized as an important link between demographic contexts and behavior because changes in the ratio shift sex-specific bargaining power in the partner market. Implicitly, the literature considers individual partner market experiences to be a function of local sex ratios. However, empirical evidence on the correspondence between subjective partner availability and local sex ratios is lacking so far. In this paper, we analyzed how closely a set of different local sex ratio measures correlates with subjective partner market experiences. Linking a longitudinal German survey to population data for different entities (states, counties, municipalities), we used multilevel logistic regression models to explore associations between singles’ subjective partner market experiences and various operationalizations of local sex ratios. Results suggest that local sex ratios correlated only weakly with subjective partner market experiences. Adult sex ratios based on broad age brackets, including those for lower-level entities, did not significantly predict whether individuals predominantly met individuals of their own sex. More fine-grained, age-specific sex ratios prove to be better predictors of subjective partner market experiences, in particular when age hypergamy patterns were incorporated. Nevertheless, the respective associations were only significant for selected measures. In a complementary analysis, we illustrate the validity of the subjective indicator as a predictor of relationship formation. In sum, our results suggest that subjective partner availability is not adequately represented by the broad adult sex ratio measures that are frequently used in the literature. Future research should be careful not to equate local sex ratios and conscious partner market experiences.

Another Gendered Demographic Dividend: Adjusting to a Future without Sons

Sonless families may pose another gendered demographic dividend. As fertility declines, families with only daughters are likely to grow. In turn, patriarchal family systems may weaken when many families are unable to engage in patriarchal practices. I examine some of these theorized dynamics in India. Sonless families did grow as fertility declined, reaching 10 percent in India as a whole in 2015 and approaching 20 percent in states with earlier fertility declines. I also identify a substantial influence of children's sex on mothers' expectations of old-age support. Using panel data from the India Human Development Survey (IHDS), I compare women's expectations after they had children to earlier expectations when they did not yet have children. Women with sons kept or further embraced patriarchal expectations that a son would provide support. Sonless mothers largely gave up patriarchal expectations, turning to daughters or away from children altogether.

The State of Sex Research in MFT and Family Studies Literature: A Seventeen-Year Content Analysis

The ability to conceptualize and treat sexual problems has been widely accepted as a crucial skill to master the MFT training. However, clients' sexual relationships are often ignored by clinicians because of a lack of experience or training, or personal discomfort. In this content analysis, we review sex and sex therapy research within MFT and family studies journals since the turn of the century. Of the 13,919 articles published within the 15 journals, 137 focused on sexuality or sex therapy. The articles were divided into five themes: sexual and relational health, sexual diversity, treatment and contributors of sexual dysfunction, sex therapy practices, and sexual education and development. Implications for clinical practices, sex therapy integration, and future research are discussed.

The association between uneven sex ratios and violence: Evidence from 6 Asian countries

It has been hypothesized that uneven sex ratios in the population could lead to increased violence. The objective of this analysis is to explore the relationship between uneven sex ratios in the population and violence. This analysis uses data collected from men in six Asian countries about their experiences and perpetration of violence. We combine this with region- and age specific sex ratios calculated from Census data to explore the relationship between sex ratios and violence using multilevel models. We find that men from region-age brackets with higher ratios of men to women are significantly more likely to report ever having raped a woman, having perpetrated intimate partner violence, or having used a weapon. We find no evidence for an association between sex ratios and reports of ever having raped a man.

High sex ratios in rural China: declining well-being with age in never-married men

In parts of rural China male-biased sex ratios at birth, combined with out-migration of women, have led to highly male-biased adult sex ratios, resulting in large numbers of men being unable to marry, in a culture where marriage and reproduction are an expectation. The aim of this study was to test the hypotheses that older unmarried men are more predisposed to depression, low self-esteem and aggression than both those who are married, and those who are younger and unmarried. Self-completion questionnaires were administered among men aged 20-40 in 48 villages in rural Guizhou province, southwestern China. Tools used included the Beck Depression Inventory, the Rosenberg's Self-esteem Scale and the Bryant-Smith Aggression Questionnaire. Regression models assessed psychological wellbeing while adjusting for socio-demographic variables. Completed questionnaires were obtained from 957 never-married men, 535 married men aged 30-40, 394 partnered men and 382 unpartnered men aged 20-29. After adjusting for socio-demographic variables, never-married men were more predisposed to depression (p < 0.05), aggression (p < 0.01), low self-esteem (p < 0.05) and suicidal tendencies (p < 0.001). All the psychological measures deteriorated with age in never-married men. In contrast, married men remained stable on these dimensions with age. Never-married men are a psychologically highly vulnerable group in a society where marriage is an expectation. Since the highest birth sex-ratio cohorts have not yet reached reproductive age, the social tragedy of these men will last for at least another generation.This article is part of the themed issue 'Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies'.

More than just climate: Income inequality and sex ratio are better predictors of cross-cultural variations in aggression

Van Lange et al. argue that variations in climate explain cross-societal variations in violence. We suggest that any approach seeking to understand cross-cultural variation in human behavior via an ecological framework must consider a wider array of ecological variables, and we find that income inequality and sex ratio are better predictors than climate of cross-societal variations in violence.

Marriage Markets and Male Mating Effort: Violence and Crime Are Elevated Where Men Are Rare

The negative social outcomes in populations with male-biased sex ratios are a growing concern. In general, the expectation is of heightened violence as a result of excess men engaging in antisocial behavior and crime, thereby threatening societal stability. While intuitive, these claims are largely unsupported in the literature. Using mating market theory as our guide, we examine indicators of male mating effort, including (1) violent competition between men (homicide, aggravated assault) and (2) indicators of uncommitted sexual behavior (rape, sex offenses, and prostitution). Our unit of analysis is U.S. county-level data. We find that counties with more men have lower rates of crime and violent behavior. Our findings challenge conventional claims of male excess leading to elevated levels of violence. Instead, in support of mating market predictions, we find that criminal and violent behavior related to male mating effort is least common in male-biased sex ratios. We discuss the implications of our findings for public policy regarding incarceration and criminal behavior.

Offspring sex preferences among patrilineal and matrilineal Mosuo in Southwest China revealed by differences in parity progression

Son preference predominates in China, yet there are patterned exceptions to this rule. In this paper, we test whether lineality (patrilineal versus matrilineal inheritance and descent) is associated with son versus daughter preference among the ethnic Mosuo (Na) of Southwest China. Our results show (i) an increased probability of continued fertility among matrilineal women after having a son compared with a daughter and (ii) an increased probability of continued fertility among patrilineal women after having a daughter compared with a son. These results are consistent with son preference among patrilineal Mosuo and more muted daughter preference among the matrilineal Mosuo. Furthermore, we show (iii) the lowest probability of continued fertility at parity 2 once women have one daughter and one son across both systems, suggesting that preferences for at least one of each sex exist alongside preferences for the lineal sex. The Mosuo are the only known small-scale society in which two kinship systems distinguish sub-groups with many otherwise shared cultural characteristics. We discuss why this, in conjunction with differences in subsistence, may shed light on the evolutionary underpinnings of offspring sex preferences.

DEMOGRAPHIC OPPORTUNITY AND THE MATE SELECTION PROCESS IN INDIA

We merged individual-level data from the 2004-2005 India Human Development Survey with district-level data derived from the 1991 and 2001 Indian population censuses to examine how the numerical supply of men to which married women were exposed during late adolescence is associated with women's agency in the mate selection process and the duration of courtships. Multilevel models that control for an array of both individual and contextual factors showed that exposure to a relative surplus of potential mates is associated with a higher likelihood that women will have little or no say in the selection of their husband and an increased probability that women will meet their husband for the first time on their wedding day. Women's educational attainment, birth cohort, religion, caste, and region of residence also emerged as significant correlates of women's marital agency and courtship duration. The implications of these findings for India's growing sex ratio imbalance are discussed.

Social context and sexual intercourse among first-year students at selective colleges and universities in the United States

Most examinations of sexual behavior ignore social context. Using panel data from the National Longitudinal Study of Freshmen, a panel study of 3924 students at 28 selective colleges and universities, I examine how institutional and peer-group characteristics influence the incidence of sexual intercourse among students during their freshman year. Students who enter college as virgins are more likely to have sexual intercourse on campuses where women comprise a higher proportion of the campus population and on campuses that are more academically rigorous. Students who had sex prior to college are less likely to have sex in college when campuses are more residential. Moreover, having friends who value religion and partying affects the likelihood that a student will have sex irrespective of their prior virginity status. These findings highlight the importance of social context for sexual behavior among college students and in the general population.

THE CONSEQUENCES OF INDIA'S MALE SURPLUS FOR WOMEN'S PARTNERING AND SEXUAL EXPERIENCES

Data from the third wave of India's 2005-2006 National Family and Health Survey are used to examine the influence of the community-level sex ratio on several dimensions of women's partnering behavior and sexual experiences. Multi-level logistic regression models that control for individual demographic attributes and community-level characteristics reveal that the local male-to-female sex ratio is positively and significantly associated with the likelihood that women marry prior to age 16 and have experienced forced sex. These associations are modest in magnitude. However, no significant associations are observed between the sex ratio and whether women have had two or more lifetime sexual partners or women's risk of contracting a sexually-transmitted disease. Birth cohort, education, religion, caste, region, urban residence, and several community-level measures of women's status also emerge as significant predictors of Indian women's partnering and sexual experiences. The implications of our results for India's growing surplus of adult men are discussed.

Skewed sex ratios and criminal victimization in India

Although substantial research has explored the causes of India's excessively masculine population sex ratio, few studies have examined the consequences of this surplus of males. We merge individual-level data from the 2004-2005 India Human Development Survey with data from the 2001 India population census to examine the association between the district-level male-to-female sex ratio at ages 15 to 39 and self-reports of victimization by theft, breaking and entering, and assault. Multilevel logistic regression analyses reveal positive and statistically significant albeit substantively modest effects of the district-level sex ratio on all three victimization risks. We also find that higher male-to-female sex ratios are associated with the perception that young unmarried women in the local community are frequently harassed. Household-level indicators of family structure, socioeconomic status, and caste, as well as areal indicators of women's empowerment and collective efficacy, also emerge as significant predictors of self-reported criminal victimization and the perceived harassment of young women. The implications of these findings for India's growing sex ratio imbalance are discussed.

Too many men: the violence problem?

There is a strong intuitive expectation in both popular lore and conventional evolutionary thinking that more males lead to more violence. Here, we untangle the logic behind this widely held notion with a specific focus on humans. We first review the relation between the intensity of sexual selection in human populations and the adult sex ratio (ASR), and find that it is more in line with recent reformulations of sexual selection theory than with conventional models. We then turn directly to the patterning of violence across human societies in relation to the sex ratio. Although the 'more men, more violence' expectation is not met, it is clear that the patterning of violence is undertheorized and we offer recommendations for steps forward.

THE EFFECT OF A MALE SURPLUS ON INTIMATE PARTNER VIOLENCE IN INDIA

Theories of the social consequences of imbalanced sex ratios posit that men will exercise extraordinarily strict control over women's behaviour when women's relationship options are plentiful and men's own options are limited. We use data from the third wave of the Indian National Family and Health Survey, conducted in 2005-06, to explore this issue, investigating the effect of the community sex ratio on women's experience of intimate partner violence in India. Multilevel logistic regression models show that a relative surplus of men in a community increases the likelihood of physical abuse by husbands even after adjusting for various other individual, household, and geographic characteristics. Further evidence of control over women when there is a sex ratio imbalance is provided by the increased odds of husbands distrusting wives with money when there is a male surplus in the local community.

High adult sex ratios and risky sexual behaviors: a systematic review

Background

Thirty-four countries worldwide have abnormally high sex ratios (>102 men per 100 women), resulting in over 100 million missing women. Widespread sex selective abortion, neglect of young girls leading to premature mortality, and gendered migration have contributed to these persistent and increasing distortions. Abnormally high adult sex ratios in communities may drive sexually transmitted disease (STD) spread where women are missing and men cannot find stable partners. We systematically reviewed evidence on the association between high community sex ratios and individual sexual behaviors.

Methods and Findings

Seven databases (PubMed, Web of Science, Embase, Scopus, The Cochrane Database of Systematic Reviews, Sociological Abstracts, and PopLINE) were searched without restrictions on time or location. We followed PRISMA guidelines and evaluated quality according to STROBE criteria. 1093 citations were identified and six studies describing 57,054 individuals were included for review. All six studies showed an association between high community sex ratios and individual sexual risk behaviors. In high sex ratio communities, women were more likely to have multiple sex partners and men were more likely to delay first sexual intercourse and purchase sex. Only two studies included STD outcomes.

Conclusions

High community sex ratios were associated with increased individual sexual risk behavior among both men and women. However, none of the studies examined unprotected sex or appropriately adjusted for gendered migration. Further studies are needed to understand the effect of community sex ratios on sexual health and to inform comprehensive STD control interventions.

INDIA'S 'MISSING WOMEN' AND MEN'S SEXUAL RISK BEHAVIOR

Although scholars and policymakers have long been concerned with the "missing women" of India, little rigorous research has examined the consequences of India's sex ratio imbalance for young men's sexual risk behavior and reproductive health. We use data from the third wave of India's 2005-2006 National Family and Health Survey to examine the influence of the community female-to-male sex ratio at ages 10 to 39 on men's likelihood of marrying early in life, of engaging in premarital, multi-partnered, and commercial sex, and of contracting a sexually-transmitted disease (STD). We estimate logistic regression models that control for respondents' demographic and socioeconomic status and that adjust for the clustering of observations within communities. Net of the effects of other characteristics, the female-to-male sex ratio is positively and significantly associated with the likelihood that men marry prior to age 18 and inversely and significantly associated with the odds that men have had intercourse with a commercial sex worker. However, no significant net associations are observed between the sex ratio and the other outcomes. Education, wealth, religious affiliation, caste, and geographic region emerge as significant predictors of Indian men's sexual risk behaviors.