Warning: these figures indicate the number of cases found in the data file. They cannot be interpreted as summary statistics of the population of interest.
Whether the interval between the birth and the previously reported birth was four or more years. This calculation is performed by the interviewer, purely in terms of years, ignoring the month of birth of each of the children. For example, a birth in April 1988 would be categorized as being four or more years after a birth in October 1984, even though there is actually less than four years between the births.