Zexuan Liu

如何构建有效测算中国专利质量的方法体系，既是该领域的前沿问题之一，也是事关中国如何全面落实创新驱动发展战略的基础性工作。本文利用1985—2021年期间中国发明专利文本信息，运用自然语言处理方法，在计算符合中国专利间文本相似度这一核心指标的基础上，探讨了适用于中国专利数据特征的专利质量测算方法。各项可靠性检验均验证了本文设计和测算的专利质量指标变量相较于传统专利质量指标的优势。基于这一专利质量指标，本文从专利申请人类型、地域分布和技术分类等角度梳理和归纳了中国1991—2016年期间中国专利质量水平的变化趋势，揭示了中国专利质量全面提升的重要特征事实。在此基础上，利用包含专利质量和数量变化的GDP增长分解框架，探究专利质量上升对中国经济增长的贡献度，发现样本期间内专利质量对经济增长的平均贡献度约为3%，且其对经济增长的作用相较专利数量呈逐步增强态势。本研究既可为有效评估各类微观主体的专利真实市场价值和自主创新能力提供基础性的识别工具，更可为中国一系列专利制度改革政策及各类科技创新激励政策的绩效评估提供参考依据。

We investigate the effect of the computer adoption rate, referred to as computerization, on the proportion of unincorporated self-employed individuals within the US labor markets. The conceptual framework suggests that computerization may either augment or diminish this share. Employing a Bartik instrument approach, we disentangle the causal effect of computerization on unincorporated self-employment from 1990 to 2010. Our empirical findings indicate that a 1% increase in computerization corresponds to a 0.79% reduction in the unincorporated self-employment share.

Autor and Dorn (Am Econ Rev 103(5): 1553–1597, 2013) provide an explanation of the polarization of US employment and wages for the period 1980–2005. Using the 1980 Census and 2005 American Community Survey data, this study replicates the estimation results of Autor and Dorn (2013) for employment polarization in all major occupation groups and qualitatively matches the wage polarization results. Also, we investigate the puzzle of why employment and wages changed in opposite directions only in clerical and administrative support occupations among three high routine task-intensive occupations.

We investigate incumbents’ pricing and nonpricing responses to product entry in market with vertical product differentiation. Using data from international airline markets, we observe price reductions by connecting incumbents in response to high-quality (nonstop) entry. We also find evidence of product repositioning (increases in total itinerary distance) by connecting incumbents. However, we do not observe significant policy changes by incumbents offering nonstop flights. Additional evidence suggests that the reason for the response by connecting incumbents is the opportunity cost of connecting at desirable airports such as airline hubs.

Breastfeeding has significant health and human capital effects on both mothers and infants. However, breastfeeding rates vary significantly within and across countries as societal, political, economic and cultural factors along with individual choices shape the breastfeeding practices. Using data from the Egyptian Demographic and Health Surveys, this study examines the effects of first motherhood timing, availability of breastmilk substitutes, and mothers’ education levels on breastfeeding duration in a major developing country, Egypt. The empirical analysis, which corrects for the estimation errors that plagued previous research, shows that delaying the first motherhood timing and increasing the availability of infant formulas have statistically significant negative effects on breastfeeding duration. Furthermore, breastfeeding duration is found to be decreasing in mothers’ education levels.