Twins, income, and happiness: Evidence from China.

We estimate the causal effect of income on happiness using a unique dataset of Chinese twins. This allows us to address omitted variable bias and measurement errors. Our findings show that individual income has a large positive effect on happiness, with a doubling of income resulting in an increase of 0.26 scales or 0.37 SDs in the four-scale happiness measure. We also find that income matters most for males and the middle-aged. Our results highlight the importance of accounting for various biases when studying the relationship between socioeconomic status and subjective well-being.

One-step achieving high performance all-solid-state and all-in-one flexible electrochromic supercapacitor by polymer dispersed electrochromic device strategy.

Electrochromic devices (ECD) are widely used to regulate the transmittance of sunlight by applying a small voltage, but the drawbacks like complex layer-by-layer preparation procedures and inconvenient assembling process still exist. To address these problems, gel or solution-type all-in-one ECDs were recently developed for the simple structure, however, the leakage risk and absence of flexible large-area production have limited real applications. Herein, a novel all-solid-state and all-in-one flexible ECD was reported by originally developed polymer dispersed electrochromic device (PDECD) strategy. This all-solid-state flexible ECD could be efficiently prepared only by one step of phase separation without any extra treatment, and demonstrated outstanding stability (92.1 % of original ΔT remained after 10,000 cycles), high coloration efficiency (197 cm2/C), low power consumption (86.4 µW/cm2) and satisfied response time (≤12 s). Meanwhile, the stored power in ECD during coloring process could drive a LED with excellent cyclic stability (93 % of original capacity remained after 3000 cycles), implying that ECD could also serve as an idea electrochromic supercapacitor. What'more, a reported largest viologen-based all-solid-state flexible ECD (17.8 × 13.2 cm2) with robust bending resistance (up to 1000 bending cycles) was successfully fabricated with industrial roller coating technique, which indicated the huge potential in real world.

The heritability of attitude toward economic risk.

The propensity to take risk underpins a wide variety of decision-making behavior, ranging from common ones such as asking for directions and trying out a new restaurant to more substantial economic decisions involving, for instance, one's investment or career. Despite the fundamental role of risk attitude in the economy, its genetic basis remains unknown. Using an experimental economics protocol combined with a classical twin strategy, we provide the first direct evidence of the heritability of economic risk attitude, at 57%. We do not find a significant role for shared environmental effects, a common observation in behavioral genetics that is contrary to commonly held views in economics. Our findings complement recent neuroeconomic studies in enhancing the understanding of the neurobiological basis of risk taking.

Cross-sectional schooling-health associations misrepresented causal schooling effects on adult health and health-related behaviors: evidence from the Chinese Adults Twins Survey.

Adult health outcomes and health behaviors are often associated with schooling. However, such associations do not necessarily imply that schooling has causal effects on health with the signs or magnitudes found in the cross-sectional associations. Schooling may be proxying for unobserved factors related to genetics and family background that directly affect both health and schooling. Recently several studies have used within-monozygotic (MZ) twins methods to control for unobserved factors shared by identical twins. Within-MZ estimates for developed countries are generally smaller than suggested by cross-sectional associations, consistent with positive correlations between unobserved factors that determine schooling and those that determine health. This study contributes new estimates of cross-sectional associations and within-MZ causal effects using the Chinese Adults Twins Survey, the first study of its type for developing countries. The cross-sectional estimates suggest that schooling is significantly associated with adult health-related behaviors (smoking, drinking, exercising) but not with own or spouse health outcomes (general health, mental health, overweight, chronic diseases). However, within-MZ-twins estimators change the estimates for approximately half of these health indicators, in one case declining in absolute magnitudes and becoming insignificant and in the other cases increasing in absolute magnitudes. Within-MZ estimates indicate significant pro-health effects for at least one of the indicators for own health (better mental health), own health-related behaviors (less smoking) and spouse health (less overweight).

Early Health Shocks, Intra-household Resource Allocation and Child Outcomes.

An open question in the literature is whether families compensate or reinforce the impact of child health shocks. Discussions usually focus on one dimension of child investment. This paper examines multiple dimensions using household survey data on Chinese child twins whose average age is 11. We find that, compared with a twin sibling who did not suffer from negative early health shocks at ages 0-3, the other twin sibling who did suffer negative health shocks received RMB 305 more in terms of health investments, but received RMB 182 less in terms of educational investments in the 12 months prior to the survey. In terms of financial transfers over all dimensions of investment, the family acts as a net equalizer in response to early health shocks for children. We estimate a human capital production function and establish that, for this sample, early health shocks negatively affect child human capital, including health, education, and socioemotional skills. Compensating investments in health as measured by BMI reduce the adverse effects of health shocks by 50%, but exacerbate the adverse impact of shocks on educational attainment by 30%.

An economic analysis of life expectancy by gender with application to the United States.

This paper presents an economic model to explain the behavior of life expectancy of both sexes. It explicitly examines the relationship between the gender gap in life expectancy and the gender gap in pay. It shows that as the latter narrows over the course of economic development, the former may initially expand but will eventually shrink. Simulation results from our model accord with the behavior of life expectancy for both sexes since the 1940s in the United States.

Estimating the effect of the one-child policy on the sex ratio imbalance in China: identification based on the difference-in-differences.

In China, the male-biased sex ratio has increased significantly. Because the one-child policy applies only to the Han Chinese but not to minorities, this unique affirmative policy allows us to identify the causal effect of the one-child policy on the increase in sex ratios by using a difference-in-differences (DD) estimator. Using the 1990 census, we find that the strict enforcement of the one-child policy led to 4.4 extra boys per 100 girls in the 1980s, accounting for about 94% of the total increase in sex ratios during this period. The robust tests indicate that the estimated policy effect is not likely confounded by other omitted policy shocks or socioeconomic changes. Moreover, we conduct the DD estimation using both the 2000 census and the 2005 mini-census. Our estimates suggest that the one-child policy resulted in about 7.0 extra boys per 100 girls for the 1991-2005 birth cohorts. The effect of the one-child policy accounts for about 57% and 54% of the total increases in sex ratios for the 1991-2000 and 2001-2005 birth cohorts, respectively.

The quantity-quality trade-off of children in a developing country: identification using Chinese twins.

Testing the trade-off between child quantity and quality within a family is complicated by the endogeneity of family size. Using data from the Chinese Population Census, we examine the effect of family size on child educational attainment in China. We find a negative correlation between family size and child outcome, even after we control for the birth order effect. We then instrument family size by the exogenous variation that is induced by a twin birth and find a negative effect offamily size on children's education. We also find that the effect of family size is more evident in rural China, where the public education system is poor. Given that our estimates of the effect of having twins on nontwins at least provide the lower bound of the true effect of family size, these findings suggest a quantity-quality trade-off for children in developing countries.