Greg Town
Project 1
10-2-01
Marriage and Divorce Rates
In less than nine months from now I
will be getting married. It's a big step in life but I know we
will be able to handle it. So with this pressing closer and
closer I wanted to see trends in marriages and divorces in the nation's
past, and if there has been any increase or decrease in either. I
also wanted to see if there was a yearly pattern to marriages and
divorces in the state of Michigan.
Part 1: National
Marriagei and Divorceii Rates
The data found on the National Center
of Health Statistics of the Center for Disease Control are shown in the
graph below. The provided data goes from 1940 to 1990.
Graph 1: The lower plot represents divorce rate and the upper
plot represents
marriage rate. The large peaks on the left of the graph took place in
1946.
It is obvious that the average marriage rate (10.39 with standard
deviation of 1.48) is higher than the average divorce rate (3.47 with
standard deviation of 1.18). But when looking at the whole picture it
would be nice to know if there is a trend happening with the rates over
the past fifty years. With marriages the regression equation is figured
to be
Marriage Rate = 84.6 - 0.0378(Year),
this has a correlation of -0.381.
With the divorces the regression equation is figured to be
Divorce Rate = -120 + 0.0628(Year),
this has a correlation of 0.79.
If looking at the overall trend over the fifty-year span it is seen
that the marriage rate is decreasing (shown by the negative slope), and
the divorce rate is increasing (positive slope). However, the
correlations are not very high so the relationship is not very strong.
One trend that sticks out is that the
same changes occur in both sets of data at the same time, but the
divorce rate changes are always less dramatic than the marriage rate
changes. This can be seen in the jump of 1946, in the slow increase
between 1963 and 1973, and in the slow decrease between 1980 and 1990.
Part 2: Number of
Marriages and Divorces in Michigan in the months of 1997 and 1998iii
When looking at just the trends in
Michigan in 1997 and 1998 the following time series plot can be seen.
Graph 2: The solid
line represents marriages and the dashed line represents divorces.
This time series plot shows the trends through time from the beginning
of 1997 to the end of 1998. The average number of marriages per month
is 5538 with a standard deviation of 2429. The average number of
divorces per month is 3226 with a standard deviation of 486.4. As you
can see the number of marriages fluctuates greatly from month to month
while the number of divorces remains relatively constant, this is
verified by the standard deviations.
To see if there is a trend in the
average number of marriages and divorces in each specific month the
following graph was made.
Graph 3:
Solid line represents average marriages and dashed line represents
average divorces.
This graph shows that there is a trend in marriages through the year. A
majority of marriages occur from June to October and the minority of
them occur in January and February. When looking at the divorces
through the year, there is not a huge fluctuation and I would predict
that if more data were available that this line would be close to horizontal through the
year.
In conclusion, one can see that
monthly the amount of marriages fluctuates greatly. However, compared
to the national yearly rates it is seen that there is little change from year to year. On the other
hand, divorces seem to remain constant through the months of the year
while also remaining constant from year to year with only a slight
increase in the past fifty years.
References
iNational Center of Health Statistics.
Center for Disease Control and Prevention. 24 September 2001
<http://www.cdc.gov/nchs/fastats/pdf/4312s-tl.pdf>
iiNational Center of Health Statistics.
Center for Disease Control and Prevention. 24 September 2001
<http://www.cdc.gov/nchs/fastats/pdf/43-9s-t 1.pdf>
iiiNational Center of Health Statistics.
Center for Disease Control and Prevention. 24 September 2001
<http://www.cdc.gov/nchs/datawh/statab/unpubd/nvsrtabl.htm#marriage&divorce>
