A data frame with 12169 observations the lengths (in years) of birth
intervals for 1859 married women with at least one birth. The first
interval (parity = 0
) is the interval from marriage to first birth.
id
Personal identification number for mother.
parity
Time order of birth interval for the present
mother. The interval with parity = 0
is the first, from
marriage to first birth.
age
The age of mother at start of interval.
year
The calendar year at start of interval.
next.ivl
The length of the coming time interval.
event
An indicator for whether the next.ivl
ends in a new birth (event = 1
) or is right censored
(event = 0
). Censoring occurs when the woman ends her
fertility period within her first marriage (marriage dissolution
or reaching the age of 48).
prev.ivl
The length of the previous time interval. May
be used as explanatory variable in a Cox regression of birth intervals.
ses
Socio-economic status, a factor with levels
lower
, upper
, farmer
, and unknown
.
parish
The Skelleftea region consists of three
parishes, Jorn, Norsjo, and Skelleftea.