What can we learn from Vital Statistics about the determinants of weekend births and male births? Prepared for Presentation at the Offord Centre for Child Studies 4 February 2015 Byron G Spencer

Many Data Sets in the RDC E.g., Vital Statistics – an administrative database Live births; deaths Close to universal coverage Application of the Birth file I’ll focus on the management and analysis of this large file (≈375K/yr) An early concern was to check for missing data and other problems E.g., the files go back to 1974, but some variables not well reported, especially in the early years ‘Place of birth’ missing for 25% of births before 1990

Vital Statistics – Births Information is limited: Event itself: When (to the day) Where (name of city/town/village, census subdivision) Place (hospital, home, other) Number of children in this event Number stillborn For each live born child – Sex Birth order Duration of pregnancy Weight Attendant (MD, RN, midwife, other, unknown)

…file content (cont’d) Mother’s Age Birthplace (province; country) Usual residence (postal code) Marital status (single, married, divorced, separated) Number of children ever live born Number of children ever stillborn Father’s Age Birthplace (province; country) Parent’s Marital relationship (married to each other?)

Weekend births If nature had its way, one-sevenths of births, 14.3 percent, would occur on each day of the week

… but that is not what happens

What can we learn from the VS records? WB = f(DUR, WT, SEX, MULT, AGE, PARITY, STILL, IMM, HOSP, PROV, MONTH, YEAR) where:WB – = 1 if birth occurred on the weekend; 0 if on weekday DUR – duration of pregnancy (5 categories) WT – birth weight (x categories) SEX – = 1 if child is male; 0 if female MULT – = 1 if more than one birth at this event; 0 if not AGE – age of mother (7 categories) PARITY – birth parity (4 categories) STILL – = 1 if previous stillbirth; 0 otherwise IMM – = 1 if mother born outside Canada; 0 otherwise HOSP – = 1 if not born in hospital; 0 otherwise PROV – place (usually province) of birth (13 categories) MONTH – month of birth (12 categories) YEAR – year of birth (10 categories)

More likely to happen on weekends – Single births – almost 5 percentage points more likely than multiple births Early births percentage points more likely if <35 wks rather than 40+ Younger mothers – 3.7 percentage points more likely if under 20 rather than 45 or older No prior still birth – 1.2 percentage points more likely First births – 3 percentage points more likely than second or higher order births Births outside of hospitals (a very small proportion of the total) About 4 percentage points more likely, or about equally likely to occur on any day of the week Immigrant women – 1.1 percentage points more likely

What about the probability of a male birth?

… with Canadian birth data we ask Is there evidence of sex-selection? Specifically among immigrants?

Equation estimated -- M = f(AGE, STILL, PARENTCoB, PROV, YEAR) where:M – = 1 if male birth; 0 if female AGEmother – age of mother (7 categories) AGEfather – age of father (7 categories) STILL – = 1 if previous stillbirth; 0 otherwise PARENTCoB – = 1 if both parents born in country j; 0 otherwise PROV – place (usually province) of birth (13 categories) YEAR – year of birth (10 categories)

Variants The equation is estimated with the observations restricted as follows First or later birth Second or later birth Third or later birth Fourth or later birth

Here is a summary of the results

Male/Female Birth Proportions by Birthplace of Parents and Number of Births