"In research in recent years, the co-authors of this article have discovered that changes in PDD [patterns of disease and death] in urban and rural areas [in China] follow to a large degree an identical pattern except for a difference in the timing of these changes (approximately 5 to 10 years).  This study is based on statistics obtained in 14 cities with a population of more than one million, complete registration systems and higher data reliability.  It is intended to ascertain how the pattern of deaths by diseases changes, and to predict the tendency of such changes through dynamic research on such patterns in those cities."  The authors analyze changes in specific causes of death and their impact on life expectancy in China.