It is unclear to what extent age structure and testing rate explain the differences in mortality rate of COVID19 across countries. Based on the agespecific data of Italy, Spain, China, and South Korea from March 23 to April 27, 2020, this paper uses decomposition method to study the differences and influencing factors for mortality rate of COVID-19 among these countries. Major findings are as follows: (1) Differences in mortality rate and fatality rate vary across countries, and are widen over time. (2) Mortality rates in Italy, Spain, and China are higher than those in South Korea. Age structure effect accounts for 66.62%, 74.82%, and 11.70% of the total difference for Italy, Spain, and China respectively. (3) After introducing relative risk in decomposition, the age structure effect for Italy and Spain, and the agespecific fatality effect for China are reduced gradually.(4) After introducing testing rate in decomposition, the effect of age structure is decreased drastically, and the positive rate of COVID-19 dominates the differences in mortality across countries. (5) The effect of testing rate on mortality for Italy, Spain, and South Korea increases over time.

The impact of intergenerational relation on living arrangement is examined using data from 2007 and 2010 Jiangsu Surveys． Results show that，first of all，most married children live with their parents and only 30% of them live independently，and there are more urban than rural married children living inde-pendently． Secondly，generational exchange desire increases the possibility to live together for both married children and their parents． Thirdly，the need to care grandchildren plays a bigger role in living together than the need to care parents． Changes of living arrangement are determined mainly by the condition of baby care． Changes of living arrangement has not been responding to changes of the elderly care desire． Home － living － based care for the elderly is facing challenges in this aging society．