1990 POPULATION CENSUS Detailed data based on a 2 per cent representative sample (1992)

V. EXPLANATION OF CONCEPTS

FERTILITY Fertility means the frequency of childbirths of females aged 15 years and over and, respectively, the number of their liveborn children, inclusive of the children deceased in the meantime, but without the number of adopted or foster children. The population census establishes the fertility of females on the basis of the totál number of their children born alive till the census moment. The data of the 1960 and earlier population censuses include the number not only of liveborn, but of all — alsó stillborn — children. Completed fertility is the fertility of females aged 50 years and over. DURATION OF MARRIAGE Duration of the marriage is the number of years elapsed from the year of the married woman's first marriage to the census moment, regardless the duration of probable separation or of the date of the second, and later marriages. EDUCATIONAL ATTAINMENT The educational attainment of the population was established on the basis of the highest educational attainment acquired within the framework of the school system. Those having completed the generál school and those with a higher educational level were ranked according to their highest completed grade and qualification, respectively. At present, the following educational institutions belong to the school system: first level schools: — generál school — institution for the education of handicapped children second-level schools: — secondary school (grammar school, secondary specialized school) — sanitary vocational school — vocational school for shorthand-typing — apprentice school — soecial vocational school third-level educational institutions: — university — college — college for kindergarten teachers. The ranking within the levels reflects the decreasing level of the institutions. The auxiliary grades, and the grades keeping the pupils occupied and the extension grades of the institutions for the education of handicapped children are of the same value as the corresponding grades of the generál school. The special vocational school is an educational institution established for the secondary training of the handicapped. Those having acquired a certificate here are indicated among those having completed a second-level apprentice school. The presentation of the data of the educational attainment does not follow the changes in the level of the educational institutions: each person's educational attainment data correspond to the level which 254