A major problem in interpreting data from Central Asia stems from the difficulties involved in discerning levels and trends. The level of mortality in Central Asia is high, even if some of the published statistics do not show this. However, it is virtually impossible to describe a trend in mortality in that region with any confidence since mortality levels were certainly grossly underestimated in the past.
If one needed to make a best guess for a life table to assign to a Central Asian population, picking one consistent with the reported age-specific mortality rates of women, such as women in their 30s, would probably be the best strategy. However, this would give only a rough approximation of mortality at other ages and would usually still result in the conclusion that mortality conditions for men were better than was actually the case. We know that any real factors that influence mortality, such as smoking, alcohol consumption, and hypertension, very likely have different effects on males and females, so the use of female mortality rates as a standard is risky.
Because of the serious problems with reported age-specific mortality rates, especially for men, it seems unlikely that cause-of-death or morbidity data for Central Asia can tell us very much about trends. If our explanation for the urban-rural crossover for men is accurate, it is also likely that the selectivity of men obtaining health care in urban areas is cause-specific, which will therefore influence cause-of-death data by rural-urban residence. Whether men go to urban places for health care will relate to the complaint and thus to the cause of death if they die.
Serious attention must be paid to the registration and data collection system in order to track trends. Given our findings regarding implausibly low reported mortality in Xinjiang (China), where death reports did not come from the registration system, this is not just a question of fixing the registration system. Error in the mortality data is also strongly affected by people's knowledge and reporting of their ages. A complex approach to improving the accuracy of reporting of ages is needed; we have discussed some possible steps with Chinese statistical authorities. It would not be easy to obtain substantial improvement, but a passive approach in which one simply waits until the entire population has completed secondary education is not very compelling. And an approach that essentially ignores the problem and its effects on mortality data should also be unacceptable.
In examining levels and trends in mortality in Central Asia, compositional effects must also be taken into account. The urban parts of Central Asia are heavily populated by Russians and members of other European groups. Because of interregional and international migration, mortality rates in urban areas are subject to change as a result of changing population composition, especially as many Europeans leave Central Asia, a process that has been going on for decades (Anderson and Silver, 1989c, 1990a). Changing population composition also