War Debt and the Baby Boom

In this paper, I argue that an important cause of the postwar baby boom in the US was the dramatic reduction in government debt (via income taxation) in the two decades following WWII. A reduction in government debt (via income taxation) increases fertility by changing the tax burden of different generations. A higher current income tax increases fertility by lowering after-tax wage and therefore the opportunity cost of child-rearing (when the cost of child-rearing involves parental time). A lower government debt level implies a lower tax burden on children in the future and thus a higher lifetime utility for them, which also increases current fertility if parents have Barro-Becker type preferences (the children's utility is included in the parents' utility function). The United States government accumulated a large amount of debt from WWII. The debt-GDP ratio peaked at 108% in 1946, and the debt level was reduced significantly (via taxation) in the following two decades. The debt-GDP ratio was only 35% in 1966. In a quantitative Barro-Becker model with government debt, I show that a reduction in government debt (financed by income taxation) such as the one experienced by the postwar US can generate a significant increase in fertility, which in magnitude accounts for 48% of the postwar baby boom in the US.Fertility, Baby boom, Government debt, WWII

Social security and the rise in health spending: a macroeconomic analysis

In this paper, I develop a quantitative macroeconomic model with endogenous health and endogenous longevity and use it to study the impact of Social Security on aggregate health spending. I find that Social Security increases the aggregate health spending of the economy via two channels. First, Social Security transfers resources from the young with low marginal propensity to spend on health care to the elderly (age 65+) with high marginal propensity to spend on health care. Second, Social Security raises people's expected future utility and thus increases the marginal benefit from investing in health to live longer. In the calibrated version of the model, I show that the positive impact of Social Security on aggregate health spending is quantitatively important. The expansion of US Social Security since 1950 can account for approximately 43% of the dramatic rise in US health spending as a share of GDP over the same period (i.e. from 4% of GDP in 1950 to 13% of GDP in 2000). I also find that this positive impact of Social Security has two interesting policy implications. First, the negative effect of Social Security on capital accumulation in this model is significantly smaller than what previous studies have found, because Social Security induces extra years of life via health spending and thus encourages private savings for retirement. Second, Social Security has a significant spill-over effect on public health insurance programs (e.g. Medicare). As Social Security increases health spending and longevity, it also increases the insurance payments from these programs, thus raising their financial burden.Social Security, Health Spending, Savings, Longevity

Joint Syntacto-Discourse Parsing and the Syntacto-Discourse Treebank

Discourse parsing has long been treated as a stand-alone problem independent from constituency or dependency parsing. Most attempts at this problem are pipelined rather than end-to-end, sophisticated, and not self-contained: they assume gold-standard text segmentations (Elementary Discourse Units), and use external parsers for syntactic features. In this paper we propose the first end-to-end discourse parser that jointly parses in both syntax and discourse levels, as well as the first syntacto-discourse treebank by integrating the Penn Treebank with the RST Treebank. Built upon our recent span-based constituency parser, this joint syntacto-discourse parser requires no preprocessing whatsoever (such as segmentation or feature extraction), achieves the state-of-the-art end-to-end discourse parsing accuracy.Comment: Accepted at EMNLP 201

n+1 Dimensional Gravity duals to quantum criticalities with spontaneous symmetry breaking

We reexamine the charged AdS domain wall solution to the Einstein-Abelian-Higgs model proposed by Gubser et al as holographic superconductors at quantum critical points and comment on their statement about the uniqueness of gravity solutions. We generalize their explorations from 3+1 dimensions to arbitrary $n+1$Ds and find that the $n+1\geqslant5$D charged AdS domain walls are unstable against electric perturbations.Comment: version to appear in commun. theor. phy