DATA SOURCES

In Thailand, a registration system of vital events, namely births and deaths was first established in Bangkok in 1909 (Vichanrathakan & Arnold, 1977). The registration of births and deaths was made compulsory throughout the whole country in 1916, and registration of foetal deaths was added to the People's Registration by the Municipal Areas Act of 1936. At present, births, deaths and foetal deaths must be registered under the People's Registration Act of 1956 as amended in 1972

(Dharmasaroja, 1981:47).

However, despite its long operation, the data generated from vital registration system are generally considered incomplete. In order to measure the extent of the incompleteness as well as to obtain accurate estimates of fertility and mortality, the National Statistical Office (NSO) conducted the first Survey of Population Change (SPC) in 1964-1967. The second SPC was carried out in 1974-1977. The third SPC was undertaken in 1984-1986. However, two additional SPC's were carried out during the middle (1989) and the end period (1991) of the Sixth National

Economic and Social Development Plan (1987-1991). These two SPC's were conducted with the purpose of collecting information on demographic and socio-economic characteristics of the population and also fertility rates, mortality rates and rates of population growth. The results from the first SPC indicated that death registration was only about 63 percent complete in 1964-1966,* about 60 per cent complete in 1974-1975, and about 76 percent complete in 1984-1986. Thus, official registration figures cannot be relied on by themselves for accurate estimates of mortality.

According to the Survey of Population Change, the underregistration is not entirely attributable to lack of public knowledge of the registration system, for most persons understand the requirements of the official system, but there is little relationship between knowledge of what should be done and actual reporting of a birth or a death. Instead of ignorance or inconvenience, the major reasons for not registering vital events are the lack of motivation of the informants and the lack of acceptance by the registrars themselves of the necessity to record all events within the specified period (NSO, 1969:17).

With the increasing realization of the need for the data on population, the first official census was taken in 1911. Up to the present, the government of Thailand had conducted 9 censuses in 1911, 1919, 1929, 1937, 1947, 1960, 1970, 1980 and 1990.

In a d d i t i o n t o p e r i o d i c c e n s u s e s , a few n a t i o n a l s urv ey s p r o v i d e i n f o r m a t i o n on f e r t i l i t y , m i g r a t i o n and m o r t a l i t y . The f i r s t n a t i o n a l sample s ur ve y c a l l e d "The L o n g i t u d i n a l Study of S o c i a l , Economic and Demographic Changes" was c o ndu ct ed by t h e I n s t i t u t e of P o p u l a t i o n S t u d i e s , Chulalongkorn U n i v e r s i t y . A n a t i o n a l sample of r u r a l hous eholds was i n t e r v i e w e d i n A p r i l and May of 1969 and a y e a r l a t e r a n a t i o n a l sample of urban h o u s eh o ld s was i n t e r v i e w e d . Taken t o g e t h e r , t h e two samples c o n s t i t u t e a n a t i o n a l sample of t h e Thai p o p u l a t i o n . The r u r a l sample was r e - i n t e r v i e w e d i n A p r i l and May 1972 and t h e urban sample one y e a r l a t e r . The L o n g i t u d i n a l Study p ro v i d e d needed benchmark d a t a f o r c u r r e n t and l a t e r e v a l u a t i o n of t h e demographic c h a r a c t e r i s t i c s of t he Thai p o p u l a t i o n , t h a t i s t h e a s s e s s m e n t of f e r t i l i t y , m i g r a t i o n and m o r t a l i t y i n both b e h a v i o r a l and a t t i t u d i n a l d i me n s i on s .

The second n a t i o n a l sample s u rv ey was "The Survey of F e r t i l i t y i n T h a i l a n d " (SOFT/WFS). This p r o j e c t was conducted i n 1975 as p a r t of t h e World F e r t i l i t y Survey (WFS). The SOFT/WFS p r o j e c t was d e s i g n e d wi th f i v e major o b j e c t i v e s as f o l l o w s :

(1) t o o b t a i n d a t a on f e r t i l i t y l e v e l s , p a t t e r n s and i n f o r m a t i o n c o n c e r n i n g f e r t i l i t y b e h a v i o r as a b a s i s f o r f o r m u l a t i n g more e f f e c t i v e p o l i c i e s with r e g a r d t o p o p u l a t i o n , and economic and s o c i a l development p l a n n i n g ;

(2) to provide timely and accurate data on fertility and mortality levels and patterns, as well as factors influencing fertility;

(3) to promote the further development of demographic survey methodology, population research and the scientific study of fertility;

(4) to provide the information necessary for evaluating the effect of family planning programs on fertility;

(5) to provide internationally comparable data on fertility levels, patterns and differentials.

Several studies showed that the information gathered on the respondent's retrospective pregnancy history from the World Fertility Survey conducted in other countries has proved useful in research on the differentials of infant and child mortality (Meegama, 1980, Somoza, 1980, Arriaga, 1981, Mott, 1982, Gubhaju, 1984). Since this study will employ the data from SOFT/WFS, a briefly outline of its methodoy and data quality are as follows.