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

.

.

.

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%

.

.

.

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.