ISP 120 Class Notes

Absolute versus Relative Change

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

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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 Bosnia-Herzegovina 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%

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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.