NORTH CAROLINA STATE LIBRARY
N. C.
Doc.
JUN 1 5 1978
A Special Report Series by the N,C. Department of Human Resources, Division of
Health Services, Public Health Statistics Branch, P.0. Box 2091, Raleigh, N.C.
No. 8 February 1978
TIME VARIATIONS IN NORTH CAROLINA BIRTHS, 1974-76
Interest in patterns of vital events has prompted considerable research in
this area. Results show that factors such as season of year, day of week, and time
of day affect the occurrence of births and certain causes of mortality (1,2). Some
researchers even suggest that lunar phases influence the timing of events (3).
In light of this research, a study was conducted using North Carolina birth
data for 1974-76 to determine if differences occur in the distribution of births by
certain variables of time. Births by day of week, month and season of year, and
lunar phase were examined, and chi-square tests were applied to the data to detect
statistical significance.
Births by Day of V/eek
The maximum number of births in the United States occurs near midweek (1).
An analysis of North Carolina births for a three-year period supports this finding;
more babies arrived on Tuesday than on any other day.
Had each day of the week occurred an equal number of times during the three
years, one would expect approximately the same number of births to occur each day,
Monday through Sunday. Such, however, is not the case; even after adjustment for
an equal number of days, large disparities exist in numbers of births per day. The
weekends are particularly different from the weekdays.
Table 1 shows adjusted daily totals of North Carolina resident live births
during 1974-76. Almost 19 percent more births occurred on Tuesday than on Sunday,
the day with the fewest births. The next smallest number of births occurred on
Saturday while Friday ranked second in highest number of births.
Table X
Resident Births by Day of Week by Race
North Carolina, 1974-76
Day of
Week
Total
White
Nonwhite
Sunday
31,190
20,525
10,665
Monday
35,982
24,565
11,417
Tuesday
37,114*
25,666*
11,448*
Wednesday
35.839*
24,813*
11,026*
Thursday
35,750*
24,618*
11,132*
Friday
36,252*
25,123*
11,129»
Saturday
32,624
22,044
10,580
*A total of 157 Tuesdays, Wednesdays, Thursdays,
and Fridays occurred during 1974-76. These days
were adjusted to 156-day bases in order to main¬
tain comparability.
