On the Erdos-Sos Conjecture for Graphs on n=k+4 Vertices

The Erd\H{o}s-S\'{o}s Conjecture states that if $G$ is a simple graph of order $n$ with average degree more than $k-2,$ then $G$ contains every tree of order $k$. In this paper, we prove that Erd\H{o}s-S\'{o}s Conjecture is true for $n=k+4$.Comment: 18 page

Economic Transition and the Motherhood Wage Penalty in Urban China: Investigation using Panel Data

China’s economic transition has fundamentally changed the mechanisms for allocating and compensating labor. This paper investigates how the economic transition has affected the wage gap between mothers and childless women in urban China using panel data for the period 1990-2005. The results show that overall, mothers earned considerably less than childless women; additionally, the wage penalties for motherhood went up substantially from the gradualist reform period (1990-1996) to the radical reform period (1999-2005). The results also show that that although motherhood does not appear to have a significant wage effect for the state sector, it imposes substantial wage losses for mothers in the non-state sector. These findings suggest that the economic transition has shifted part of the cost of child-bearing and -rearing from the state and employers back to women in the form of lower earnings for working mothers.

Gender and Occupational Mobility in Urban China during the Economic Transition

This paper examines the gender patterns of occupational mobility in post-reform Urban China using a national representative dataset. The results reveal marked differences between married men and women: women are more likely than men to undergo lateral or downward occupational changes, but are less likely to experience upward mobility. The results also show that the public-sector restructuring has increased the incidence of downward occupational mobility, more for women than men. The analysis suggests that women are disadvantaged in the occupational mobility process by a variety of social and institutional factors.Occupational mobility, Gender, Economic transition, Social networks

Phenomenological discriminations of the Yukawa interactions in two-Higgs doublet models with Z2Z_2 symmetry

There are four types of two-Higgs doublet models under a discrete $Z_2$ symmetry imposed to avoid tree-level flavour-changing neutral current, i.e. type-I, type-II, type-X and type-Y models. We investigate the possibility to discriminate the four models in the light of the flavour physics data, including $B_s-\bar B_s$ mixing, $B_{s,d} \to \mu^+ \mu^-$, $B\to \tau\nu$ and $\bar B \to X_s \gamma$ decays, the recent LHC Higgs data, the direct search for charged Higgs at LEP, and the constraints from perturbative unitarity and vacuum stability. After deriving the combined constraints on the Yukawa interaction parameters, we have shown that the correlation between the mass eigenstate rate asymmetry $A_{\Delta\Gamma}$ of $B_{s} \to \mu^+ \mu^-$ and the ratio $R={\cal B}(B_{s} \to \mu^+ \mu^-)_{exp}/ {\cal B}(B_{s} \to \mu^+ \mu^-)_{SM}$ could be sensitive probe to discriminate the four models with future precise measurements of the observables in the $B_{s} \to \mu^+ \mu^-$ decay at LHCb.Comment: 29 pages, 4 tables, 11 figures. v3: minor corrections included, matches published version in EPJ

Enterprise Restructuring and Firm Performance: A Comparison of Rural and Urban Enterprises in Jiangsu Province

We examine the contrast in the experience of ownership reforms between urban SOEs and rural TVEs using a panel of industrial enterprises in Nanjing municipality for the period from 1994 to 2001. Our objectives are twofold. First, we study how the reform program of “grasp the large and let go of the small” has been carried out in practice by comparing the patterns of enterprise restructuring in the SOEs and the TVEs. Second, we investigate how the alternative reform strategy has affected firm performance in terms of the growth of labor productivity, total factor productivity (TFP), profitability, and worker earnings. We find a sharp contrast in the reform strategies of the SOEs and TVEs in two respects. First, the changes in the SOE sector were more gradual and involved more limited transfer of property rights than did the reform of the TVEs. Secondly, the reforms in both sectors exhibited selection bias but in opposite directions, with worse performing ones being the principal targets of reforms, among SOEs, and better performing enterprises being more likely to be picked for privatization, among TVEs. Our analysis discerns strikingly strong, robust positive effects of ownership restructuring on the growth of labor productivity, TFP and profitability in the reformed SOEs, indicating that the evolutionary reform policy for the SOEs has successfully reversed the trends of declining productivity and profits in these enterprises in Nanjing. We also find that among reformed urban enterprises, those in which private ownership accounts for less than 50% of shares performed better than those in which the majority of shares are owned privately. We find mixed evidence for the TVEs: privatization had no effect on firm performance in a group fixed-effects model but significant, positive effects in a firm fixed-effects model.http://deepblue.lib.umich.edu/bitstream/2027.42/40054/3/wp668.pd

The Economics of a Regulated Dairy Market: An Empirical Analysis of Factors Determining the Values of Fluid Milk Quota

Based on the hypothesis that tradeable marketing quotas may be analysed as an economic input in the production process of regulated firms, the standard capital asset pricing model is adapted to assess the impact of expectations of quota rents on Ontario fluid milk quota values. The analysis provides estimates of the marginal impacts on quota values of two variables postulated to proxy the rent that arises from the highly regulated market for this product. The results are consistent with expectations from economic theory for a divisible capital asset. It appears that the regulated marketing system for fluid milk has enabled appreciable returns from improvements in milk production technology and administered prices to be appropriated by producers. Milk production technology advances, proxied by average herd size, and increases in administered prices for milk evidently contribute to increased quota values. An experiment to assess the impact of reductions in milk prices on quota values is reported. The results of the study indicate that, following a 1 percent change in producers' price levels for milk, Ontario fluid milk quota values change by some 0.36 percent immediately and by some 6 percent over a longer-term period of about four years.Livestock Production/Industries,

Labour Migration and Time Use Patterns of the Left-Behind Children and Elderly in Rural China

Rural-urban migration has become a major feature of the Chinese economy since the mid-1990s. Due to institutional arrangements and economic and cultural factors, massive labor migration has resulted in a large left-behind population consisting of children, non-elderly married women, and the elderly. This paper examines the impacts of labor migration on time use patterns of the left-behind elderly people and children in rural China, using data derived from the China’s health and Nutrition Health Survey (CHNS) for the period between 1997 and 2006. The results show that the migration of household members increases the time spent on farm work and domestic work for the left-behind elderly, and the migration of parents increases the time spent on farm work and domestic work for the left-behind children. Importantly, migration has striking gender differentiated impacts with the increase in work time being greater for elderly women and girls than elderly men and boys. These results have important policy implications.

Enterprise Restructuring and Firm Performance: A Comparison of Rural and Urban Enterprises in Jiangsu Province

We examine the contrast in the experience of ownership reforms between urban SOEs and rural TVEs using a panel of industrial enterprises in Nanjing municipality for the period from 1994 to 2001. Our objectives are twofold. First, we study how the reform program of “grasp the large and let go of the small” has been carried out in practice by comparing the patterns of enterprise restructuring in the SOEs and the TVEs. Second, we investigate how the alternative reform strategy has affected firm performance in terms of the growth of labor productivity, total factor productivity (TFP), profitability, and worker earnings. We find a sharp contrast in the reform strategies of the SOEs and TVEs in two respects. First, the changes in the SOE sector were more gradual and involved more limited transfer of property rights than did the reform of the TVEs. Secondly, the reforms in both sectors exhibited selection bias but in opposite directions, with worse performing ones being the principal targets of reforms, among SOEs, and better performing enterprises being more likely to be picked for privatization, among TVEs. Our analysis discerns strikingly strong, robust positive effects of ownership restructuring on the growth of labor productivity, TFP and profitability in the reformed SOEs, indicating that the evolutionary reform policy for the SOEs has successfully reversed the trends of declining productivity and profits in these enterprises in Nanjing. We also find that among reformed urban enterprises, those in which private ownership accounts for less than 50% of shares performed better than those in which the majority of shares are owned privately. We find mixed evidence for the TVEs: privatization had no effect on firm performance in a group fixed-effects model but significant, positive effects in a firm fixed-effects model.China, ownership reform, privatization, SOE, TVE