ISP
120 Class Notes
There are two ways to measure change in
numerical data. One can examine either
the absolute change or the relative change.
The absolute change in numerical data is the difference between the
initial and final figures. That is, the
final amount minus the initial amount.
If the absolute change is negative, this implies a decrease from the
initial to the final amount. If the absolute change is positive, this implies
an increase from the initial to the final amount.
The relative change in numerical data is the ratio of the absolute
change relative to the initial
amount. That is, the absolute change
divided by the initial amount. Typically, this ratio is then converted to a
percentage change.
In fact, percentage change and relative
change are synonymous. If the
relative change is negative, this implies a percent decrease from the initial
to the final amount. If the relative change is positive, this implies a percent
increase from the initial to the final amount.
To study the distinction between these two different ways of measuring change, refer to the EXCEL file WorldCountryPop.xls, which lists the population of various countries in the world in 1980, 1990, and 2000. If we measure the population change of the countries from 1990 to 2000 using the absolute change, we can see which country experienced the greatest and least population change.
Notice that the Ukraine experienced the
greatest decrease in its population from 1990 to 2000. It lost 2,505,000
people. In contrast, India experienced the greatest increase in its
population from 1990 to 2000. It gained
163,446,000 people. Note: Pay
close attention to the population figures which are given in thousands.

Area 
Population (in
thousands) 


Country
or area 
(sq. mile) 
1980 
1990 
2000 
Absolute Popul Change from 1990 to 2000 
Ukraine 
233089 
50047 
51658 
49153 
2505 
Russia 
6592817 
139045 
148082 
146001 
2081 
Bulgaria 
42683 
8844 
8894 
7797 
1097 
Bosnia
and Herzegovina 
19741 
4092 
4424 
3836 
588 
.
.
.
Nigeria 
351649 
69593 
92483 
123338 
30855 
Indonesia 
705189 
154936 
188651 
224784 
36133 
China 
3600930 
984736 
1138895 
1261832 
122937 
India 
1147950 
690462 
850558 
1014004 
163446 
One can measure the population change of these countries in relative terms, also. This can be especially informative since the 1990 populations vary so much from country to country. We can measure what percent of the initial (1990) population the absolute change represents. That is, we want to form the ratio between the absolute population change and the initial (1990) population for each country. To do this, we divide the absolute population change by the initial (1990) population to find the relative population change from 1990 to 2000.
Notice below, that BosniaHerzegovina experienced the greatest percent decrease in its population. A loss of 588 thousand people reflects a 13.29% decrease in its initial (1990) population. In contrast, Afghanistan experienced the greatest percent increase in its population. Its 2000 population is 75.52% greater than its initial (1990) population.

Area 
Population ( in
thousands) 



Country
or area 
(sq. mile) 
1980 
1990 
2000 
Absolute Popul. Change from 1990 to 2000 
Relative Popul. Change from 1990 to 2000 
Bosnia
and Herzegovina 
19741 
4092 
4424 
3836 
588 
13.29% 
Bulgaria 
42683 
8844 
8894 
7797 
1097 
12.33% 
Latvia 
24903 
2525 
2672 
2405 
267 
9.99% 
Estonia 
17413 
1482 
1573 
1431 
142 
9.03% 
.
.
.
French
Guiana 
34421 
68 
116 
173 
57 
49.14% 
Jordan 
35344 
2163 
3262 
4999 
1737 
53.25% 
Qatar 
4247 
231 
481 
744 
263 
54.68% 
Afghanistan 
250000 
14985 
14750 
25889 
11139 
75.52% 
Although we can measure change in numerical data in two ways, it is generally more informative to calculate the relative change because it a quantitative measurement that is very sensitive to what the initial amount is (which is the denominator in the ratio). Think about this claim by looking at the first table above where Bulgaria experienced a smaller absolute loss in its population than Russia did. However, because Bulgaria’s initial (1990) population is so much smaller than Russia’s, the relative population change for Bulgaria is a whopping 12.33% population loss. Whereas, Russia’s percent decrease in population is only 1.4%.
Here is another look—using a more graphical approach—at the very different conclusions that can be reached when measuring numerical change according to absolute versus relative terms. Carefully compare and contrast the geographical trends of the absolute population change versus the relative population change. There are some dramatic differences to be observed here which once again highlight the distinction between the quantitative measurements of absolute change and relative change.