Notes
The best number of months or years between the birth of one child and the birth of the next child. The first digit gives the units in which the respondent answered (1 indicates months, 2 indicates years, and 9 indicates a special response), while the last two digits give the time in those units. If the units value is 9 then the variable contains a special response, and if the duration value is greater than 90 this also indicates a special response. For example, code 996 is used for " other" answers, and code 299 would mean that the response was given in years but the actual duration was missing on the questionnaire.