TABLE 3-3 Years of Primary and Secondary Schooling

 

Females

Males

Cohort

Mean

Standard Deviation

Mean

Standard Deviation

1953-1954

10.52

1.87

10.05

2.10

1955-1956

11.07

1.92

10.47

1.84

1957-1958

11.12

1.69

10.53

1.74

1959-1960

11.10

1.48

10.77

1.99

1961-1962

11.24

1.68

10.70

1.97

1963-1964

11.45

1.64

10.73

1.87

1965-1966

11.52

1.79

10.95

1.95

1967-1968

11.71

1.81

11.23

2.05

1969-1970

11.86

1.74

11.16

2.02

TABLE 3-4 Number of Children Born Until End of 1998

 

Females

Males

Cohort

Mean

Standard Deviation

Mean

Standard Deviation

1955-1956

1.68

1.01

1.71

1.18

1957-1958

1.65

1.15

1.74

1.14

1959-1960

1.80

1.05

1.59

1.22

1961-1962

1.76

1.06

1.44

1.07

1963-1964

1.64

1.10

1.39

1.12

1965-1966

1.43

1.03

1.05

1.05

1967-1968

1.11

0.98

0.75

0.90

1969-1970

0.78

0.89

0.47

0.72

across cohorts began earlier—starting for cohorts born in the late 1950s— and is more pronounced. This difference is likely to be caused by the somewhat later age pattern of childbearing and the age difference between mothers and fathers.

A potential criticism of a study of the fertility of twins is that twins are not a random draw of all children. Twins are more likely to be born prematurely and to have lower birth weights than nontwins. In this survey DZ twins were born more frequently to older mothers for the birth years covered. A close congruence between the fertility patterns of twins and those of the general population is therefore an essential precondition in order to generalize the results of twin-based investigations into biosocial determinants of fertility to the general population. In Kohler et al. (2002a)



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