June 10, 2009
The following table shows mean children ever born (CEB) from the Thailand censuses of 1960, 1970 and 1980 together with the times at which each cohort reached the mean age at childbearing, estimated to be age 30 years.
Table 1: Children Ever Born Data for Thailand: 1960, 1970 and 1980 Censuses
Sources Thailand Population Census: 1960 [25-Apr], Table 15; 1970 Population & Housing Census: Whole Kingdom [1-Apr], table 7, page 20; 1980 Population & Housing Census: Whole Kingdom [1-Apr], table 7, pages 30-31.
The time-plot of the 1960 values shown below indicates a graduate rise in completed fertility during the 1920s and 1930s. Without further evidence, this apparent rise might simply be deteriorating completeness of children ever born reporting as women age.
Time plot of CEB Data for Thailand: 1960 Census
Comparing the time plots for the 1960 and 1970 data (below) indicates that the rise in completed fertility is real. The mean children born reported by women 55-59 years old at the 1970 census is slightly below the level reported by the same cohort in the 1960 census, when they were 45-49 years old, but the difference is small (0.04 children per woman) in relation to the overall trend. The evidence suggests that completed fertility in Thailand rose from about 5.7 children per women circa 1922 to over 6.3 children per woman circa 1952, a rate of increase of about 0.2 children per woman per decade.
Time plot of CEB Data for Thailand, Censuses of 1960 and 1970
Given the consistency of the plots for the 1960 and 1970 censuses, we expect further confirmation, if perhaps a deceleration of the rise, from the 1980 data. What we observe comes as something of a shock. Far from confirming the trend, the 1980 data points for the two older age groups fall almost a full child per woman below the corresponding 1970 census points. The 10 year age groups used for the 1980 data are a nuisance for comparison, but either the women in question were greatly overstating children ever born in 1970 or greatly understating it in 1980.
Time plot of CEB Data for Thailand, Censuses of 1960, 1970 and 1980
Over statement of children ever born almost never occurs, so the clear conclusion is that children ever born were seriously underreported in the 1980 census. It is notable that the two older age groups in 1980 data confirm the rise in fertility indicated by the earlier censuses. The indication of decline after 1955 might of course be the beginning of fertility decline.
“Time-plotting Life Cycle Events,” Griffith Feeney, May 30, 2009.
“Time-plotting Children Ever Born Data for the United States,” by Griffith Feeney, May 31, 2009.
“Time-plotting Children Ever Born Data for Kenya,” by Griffith Feeney, June 1, 2009.