perceptions of illness, and the attitudes of medical staff. In addition, attendance may be determined by the type of complaint. Por example, patients may be more likely to be taken to a health care facility after an accident than with a chronic illness. Where the majority of deaths do nct occur in hospitals or clinics, health facility statistics are likely to give a very distorted picture of caubation.

Specially conducted surveys may therefore provide the most fruitful approach in the short-term. Special surveys have several advantages over alternative approaches. Firstly, it is possible to concentrate resources on obtaining data of high quality over a limited time period. It is easier to maintain high standards of training and supervision over a short time period than in a permanent routine system. Secondly, it may be feasible to develop uniform survey instruments that could be applied in parallel surveys in several countries, although some local variations might be necessary. This should allow useful comparative studies of patterns of mortality in different geographical regions. Thirdly, it is possible in a specially conducted survey to obtain information not only about mortality rates, and causes of death, but on a range of socio-economic, demographic, environmental and other factors of interest. This would allow an analysis of the determinants and consequences of adult mortality.

Two basic types of survey are possible in this context. In a single-round survey, a sample of households is visited, and questions asked about adult deaths that have occurred in the past. In a multi-round survey, the same households are visited repeatedly, so that deaths can be recorded prospectively. Single-round surveys are considered in Section 3.2, and multi-round surveys in Section 3.3.

# 3.2 Single-round surveys

# 3.2.1 Indirect demographic methods and cause-specific mortality

The most obvious method of estimating mortality rates in a single-round survey is to question the head of each household about deaths that have occurred in the household during a specified period. Experience in demographic surveys, however, has shown the use of the household head as respondent to be unsatisfactory. Under-reporting of deaths occurring during the preceding twelve months is common (Blacker, 1984), and results from several factors, including reference period errors, cultural influences leading to a reluctance to talk about deaths, and simple omissions. An additional problem is that an adult death often leads to the fission or regrouping of the household, so that the household in which the death occurred may not exist by the time of the survey.

In an attempt to overcome some of these difficulties, demographers have developed a range of techniques for the estimation of mortality rates known as "indirect methods". Using these methods, estimates of adult mortality are derived from data on the survival of close relatives, and represent averages of the mortality expcrienced over the period during which the relatives were exposed to the risk of dying (United Nations, 1983). Characteristics of the respondent, especially their age, are used in the analysis, rather than characteristic of the deceased. Asking respondents about the survival of specific relatives 12