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Are young cohorts of women delaying first birth in Mexico?


In the last decades, female permanent sterilisation became the most used method of contraception in Mexico. During this time, the demand for pills, condoms and other short-term contraceptives fell consistently. The shift in the demand for contraceptives raises concerns among demographers that the timing of children may remain unchanged regardless of observed reductions in period fertility rates. This paper assesses such ideas in the context of the timing of a first child using duration models as the main analysis tool. Findings suggest that young cohorts of women are effectively delaying first birth relative to the experience of older generations.

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  1. The total fertility rate (TFR) is a measure of the number of children that a woman would have at the end of their fertile life if she follows the current ‘typical’ fertility behaviour at all stages of her life (it can be expressed in terms of children per 1,000 women). Age-specific fertility rates indicate the number of birth per 1,000 women in different age-specific groups.

  2. Cases where the given dates of birth of mothers and their children implied a negative duration interval were excluded. The analysis is done conditional on this selection.

  3. During estimation, it was found that moving the calendar limits of the generation dummies for +5 and −5 years did not result in important changes in the estimated parameters and their standard errors.

  4. The underlying continuous time hazard θ(.) is the model the researcher would estimate if continuous time duration data were available. However, if one collects duration intervals that only change in a discrete manner (say, years) and x i is constant between t and t+1, then θ(.) can be written as h it . In the duration data literature, h it is known as the discrete time hazard function (see, for instance, Meyer 1990; Sueyoshi 1995).

  5. Notice that the Extreme Value distribution of the discrete time hazard h it is a direct consequence of the proportional hazard functional form of the underlying continuous time hazard θ(t). To avoid confusion between h it and θ(t), h it is referred to as the ‘EV hazard’ whenever θ(t) is supposed to belong with the proportional hazard family.

  6. The Extreme Value type I distribution may not be attractive in applied work because it has a fat right tail (i.e. the distribution is skewed to the right and has skewness to 1.13955). Clearly, for large samples, central limit theorem arguments would suggest that a rather symmetric distribution such as Normal is appropriate.

  7. To simplify exposition, from now on, the reader should understand ‘discrete time’ hazard anytime the hazard function is referred to.

  8. The typical individual was found to be Catholic and had 5.35 years of education at age 12.

  9. According to the ENADID, between 1992 and 1997, single mothers contributed 5% of the most recent pregnancies that resulted in live births. No single mothers are reported among non-Catholic women who were born between 1953 and 1957. In contrast, the generation of non-Catholics who were born between 1968 and 1972 contributed 8.41% of children born to single mothers. In other words, non-Catholic women in the young cohort contributed a higher proportion of out of wedlock births than non-Catholic women in the older cohort. To complete the picture, data from the ENADID show that while 78% of women in the 1953–1957 cohort married before age 25 (or entered a consensual union), only 69% of women in the 1968–1972 cohort married before that age. Clearly, these descriptive statistics support the hypothesis that, at least in relative terms, the Catholic Church is succeeding in persuading young couples to delay marriage and sexual intercourse.


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I am grateful to Wiji Arulampalam, Mark Stewart, John Ermisch, Jeremy Smith and two anonymous referees for useful comments. I am also grateful to the National Council for Science and Technology (CONACYT) for its financial support.

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Correspondence to Alfonso Miranda.

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Responsible editor: Junsen Zhang

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Miranda, A. Are young cohorts of women delaying first birth in Mexico?. J Popul Econ 19, 55–70 (2006).

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  • Timing of children
  • Duration models
  • Mexico


  • J13
  • J15
  • C41