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A line graph is often the most effective format for illustrating a relationship between two variables that are both changing. For example, time series graphs can show patterns as time changes, like the unemployment rate over time. Line graphs are widely used in economics to present continuous data about prices, wages, quantities bought and sold, the size of the economy.

How Graphs Can Be Misleading

Graphs not only reveal patterns; they can also alter how patterns are perceived. To see some of the ways this can be done, consider the line graphs of [link] , [link] , and [link] . These graphs all illustrate the unemployment rate—but from different perspectives.

All three graphs present the exact same data but in different ways that may alter how the data is interpreted. Image (a) shows the unemployment rate wide and short. Image (b) shows the unemployment rate narrow and tall. Image (c) shows the unemployment rate, with wider range of numbers on the vertical axis.

Presenting unemployment rates in different ways, all of them accurate

Image (f) shows the unemployment rate monthly data.
Simply changing the width and height of the area in which data is displayed can alter the perception of the data.

Presenting unemployment rates in different ways, all of them accurate

Image (f) shows the unemployment rate since 1975 only.
Simply changing the width and height of the area in which data is displayed can alter the perception of the data.

Suppose you wanted a graph which gives the impression that the rise in unemployment in 2009 was not all that large, or all that extraordinary by historical standards. You might choose to present your data as in [link] (a). [link] (a) includes much of the same data presented earlier in [link] , but stretches the horizontal axis out longer relative to the vertical axis. By spreading the graph wide and flat, the visual appearance is that the rise in unemployment is not so large, and is similar to some past rises in unemployment. Now imagine you wanted to emphasize how unemployment spiked substantially higher in 2009. In this case, using the same data, you can stretch the vertical axis out relative to the horizontal axis, as in [link] (b), which makes all rises and falls in unemployment appear larger.

A similar effect can be accomplished without changing the length of the axes, but by changing the scale on the vertical axis. In [link] (c), the scale on the vertical axis runs from 0% to 30%, while in [link] (d), the vertical axis runs from 3% to 10%. Compared to [link] , where the vertical scale runs from 0% to 12%, [link] (c) makes the fluctuation in unemployment look smaller, while [link] (d) makes it look larger.

Another way to alter the perception of the graph is to reduce the amount of variation by changing the number of points plotted on the graph. [link] (e) shows the unemployment rate according to five-year averages. By averaging out some of the year- to-year changes, the line appears smoother and with fewer highs and lows. In reality, the unemployment rate is reported monthly, and [link] (f) shows the monthly figures since 1960, which fluctuate more than the five-year average. [link] (f) is also a vivid illustration of how graphs can compress lots of data. The graph includes monthly data since 1960, which over almost 50 years, works out to nearly 600 data points. Reading that list of 600 data points in numerical form would be hypnotic. You can, however, get a good intuitive sense of these 600 data points very quickly from the graph.

A final trick in manipulating the perception of graphical information is that, by choosing the starting and ending points carefully, you can influence the perception of whether the variable is rising or falling. The original data show a general pattern with unemployment low in the 1960s, but spiking up in the mid-1970s, early 1980s, early 1990s, early 2000s, and late 2000s. [link] (g), however, shows a graph that goes back only to 1975, which gives an impression that unemployment was more-or-less gradually falling over time until the 2009 recession pushed it back up to its “original” level—which is a plausible interpretation if one starts at the high point around 1975.

These kinds of tricks—or shall we just call them “presentation choices”— are not limited to line graphs. In a pie chart with many small slices and one large slice, someone must decided what categories should be used to produce these slices in the first place, thus making some slices appear bigger than others. If you are making a bar graph, you can make the vertical axis either taller or shorter, which will tend to make variations in the height of the bars appear more or less.

Being able to read graphs is an essential skill, both in economics and in life. A graph is just one perspective or point of view, shaped by choices such as those discussed in this section. Do not always believe the first quick impression from a graph. View with caution.

Key concepts and summary

Math is a tool for understanding economics and economic relationships can be expressed mathematically using algebra or graphs. The algebraic equation for a line is y = b + mx, where x is the variable on the horizontal axis and y is the variable on the vertical axis, the b term is the y-intercept and the m term is the slope. The slope of a line is the same at any point on the line and it indicates the relationship (positive, negative, or zero) between two economic variables.

Economic models can be solved algebraically or graphically. Graphs allow you to illustrate data visually. They can illustrate patterns, comparisons, trends, and apportionment by condensing the numerical data and providing an intuitive sense of relationships in the data. A line graph shows the relationship between two variables: one is shown on the horizontal axis and one on the vertical axis. A pie graph shows how something is allotted, such as a sum of money or a group of people. The size of each slice of the pie is drawn to represent the corresponding percentage of the whole. A bar graph uses the height of bars to show a relationship, where each bar represents a certain entity, like a country or a group of people. The bars on a bar graph can also be divided into segments to show subgroups.

Any graph is a single visual perspective on a subject. The impression it leaves will be based on many choices, such as what data or time frame is included, how data or groups are divided up, the relative size of vertical and horizontal axes, whether the scale used on a vertical starts at zero. Thus, any graph should be regarded somewhat skeptically, remembering that the underlying relationship can be open to different interpretations.

Review questions

Name three kinds of graphs and briefly state when is most appropriate to use each type of graph.

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What is slope on a line graph?

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What do the slices of a pie chart represent?

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Why is a bar chart the best way to illustrate comparisons?

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How does the appearance of positive slope differ from negative slope and from zero slope?

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Questions & Answers

start a new proponda of ECONOMIC ALLIANCES YOU are Ready
Javid Reply
start a new conversation
Madhu Reply
may anyone guide me how the financial market is linked to economics? in detail? and in simple language?
Gopal Reply
economics is all about money matter .where we use money has medium of exchange.
Madhu
Economics means optimim utilization of related factors which can be measured only by time and money
Rakesh
can anyone suggest how to put questions here?
Gopal Reply
Go on any topic for example perface
Rakesh
Then go at last and write in new conversation
Rakesh
why demand and supply equal
Ashitosh Reply
Demand equal to supply coz if supply more then price less and if price less then demand more also opposite​
Rakesh
M i right ?
Rakesh
if supply will be more then the demand, then price will fall down. same with the demand. if the demand is high, then price of the product will rise.. and equilibrium happens when both supply and demand are at equal level.
Gopal
ok thanks
Gopal
if supply is more we can store it . when the food scricty will not occur...
Madhu
and also there is group called fci(food coupration of India.)whenever there is food sacricty this council will provide food for needy people.
Madhu
If supply more then no any want to store because price will be less
Rakesh
Also can not store some products such as electricity.. Milk.. Fruits and vegetables and network
Rakesh
what is the scope of being an economist?
sheraz Reply
what is the scope of economics?
sheraz
Economies of scope is a term that refers to the reduction of per-unit costs through the production of a wider variety of goods or services.
Cette
good
Kranti
great
sheraz
but Cette I meant something else...
sheraz
I mean where can an economist find a job? I mean in which fields?
sheraz
u can work as research analyst and business consultant.
Gopal
market research analyst i mean to say.. u can find jobs in such as Deloitte, KPMG, JP morgan, or any other market research company. u can find it on google by just typing market research companies in your country
Gopal
U can decide to print amount of money .. Can decide the budget and can understand share market .. Means jobs anywhere to understand market trends means companies are going to long term benefits with social welfare with maximum utilization of related factors
Rakesh
Does trade war effect world economy growth?
Yes,it does
Madhu
yh it will
Cette
yup
sheraz
Yes it will create more problems to economy like food sacricty. and it affects towards production and loss through our national income or GDP.
Madhu
what is the difference between explicit cost and implicit cost
ustaz Reply
explicit cost:it is the cost which company made for purchasing or hiring resources from the factor owner. implicit cost : the cost of the owner of the company pay for the project.
دولت
explicit cost is that cost which is identified by the books of accounts of an organisation
Amulya
implicit cost is that cost which is not shown in the books of accounts but due to this cost organisation gets some benefits
Amulya
what is supply
Motunrayo
The willing and able to sells their goods in various price of a commodity is called supply.
Niraj
what are the laws of supply
Motunrayo
what is lonrenzo curve
osidele
What is price elasticity of demand?
Kanishka Reply
price elasticity of demand is a measure used in economics to show elasticity of quantity demanded of good or service to get a change in it's price while nothing but price changes.
Madhu
Price elasticity of demand is a measure of the change in the quantity demanded of a product in relation to its price change Price elasticity of demand = % change in quantity demand / % change in Price
Gaurav
Pls where can I found PRICE CONTROL on this app
Samuel Reply
top left corner
JUDE
A situation in an economy with one producer but many consumers
Kabali Reply
What is the theory of population according to Malthus?
Kabali
What is the Malthusian population theory?
Kabali
The Malthusian theory of population state that, where there are means of substinence like food, human beings have the tendency to procreate (ie.give birth) without restraint (ie. control).
George
he stated that population unchecked grows at a geometric progression ie 1,2,4,8,16 while the means food subsistence grows at arithmetic progression ie 1,2,3,4,5---- he declared that population has the tendency to outstrip the means of subsistence
Fung
What is money?
Kabali
money is any commodity that act as a medium of exchange
Fung
money is medium of exchange which is use in taking goods and giving some of it's worth or money value
Madhu
what is a debit card and a credit card?
Milly
a debit card is a payment card used instead of cash while purchasing
Madhu
a credit card is a payment card issued to users to enable cardholder to pay a merchant for goods and services
Madhu
oky tanx
Milly
good
ABDUL
What is an inferior good.?
Kabali
In economics, an inferior good is a good whose demand decreases when consumer income rises (or demand rises when consumer income decreases), 
Rams
in that case scarcity of food will occur
Madhu
what is monopoly
Richmond Reply
a market situation when there is only one seller of a product representing whole industry.
how
where one business is the dominant one in that market. It determines the market price as they are price makers. No entry, no competition.
karl
it is a market situation where is a single seller and many buyer hear the seller is the price maker the is no free entering and exit in this market
Fung
A situation in the economy where there is one producer and many consumers
Kabali
A market situation where there is one producer and many consumers.
Kabali
Balance of payments for 2018
Mahlatse Reply
what is monopoly and what is monopolaist
Javid Reply
what is the affect of rise in value of dollar ?
Shabana
monopoly"a single firm or company owns all or nearly all of the market for a given type of product or service "monopoly is a price maker ...barrier of entry ,non availability of close substitute.
Shabana
monopolistic competition or market is a situation where there are few or many firm producing identical but differentiated product .eg difference in advertisement ,packing etc
Shabana
monopolistic competition or market is a situation where there are few or many firm producing identical but differentiated product .eg difference in advertisement ,packing
jay
monopoly is a market situation ...where there is a single seller and large number of buyers deals with commodities having no close substitutes......here the sellers are price makers... there is restrictions in the entry and exit of new firms in this market structure....
lovely
what is money?
Hilary
money is a medium of exchange.....through which...commodities are bought and sold
lovely
money is a medium/means of exchange that generally accepted by law
Prince
What is tranfer earnings
Admire
what is savings income?
Limitles
transfer earning is the minimum income that a factor is willing to accept in an occupation,it is also call the supply price of a factor
Fung
what is envelope curve
Dharam
what is depreciation
Fung
depreciation means decrease in value of a assets due to normal wear or year ,means decrease in value of assets like a machine due to its daily use
ru
Refers to wear and tear of capital machinery
apule
what is meant by currency depreciation?
Shabana
an envelope curve is also call an umbrella curve it is any curve that is enclosed by being tangen t to a series of other curves
Fung
fall in the value of currency vis-a-vis any other currency usually $ due to marker forces is called currency depreciation. it is different from devaluation where in value of currency is deliberately reduced to improve BoT
mohammad
depreciation in its broad sense means loss in the value of fixed capital say a tractor due to i) normal wear and tear ii) normal rate of accidental damage iii) expected absolescence to meet this, Depereciation Reserve Fund is created it is calculated by firms on the basis of their experience.
mohammad
what is green revolution ?discuss the achievement of green revolution in India
Sweety Reply
green revolution is the third revolution of agricultural refers to a set of research and development of technology transfer initiative occuring between 1930s and the late 1960s that increased agricultural is called green revolution
Javid
the green revolution happened because to improve the agricultural sector towards adopting mordern methods and improvement of agricultural equipments
Madhu
green revolution means new innovation for high yielding varieties seeds towards economic development in agriculture sector. started in 1966, it's achievement increase per productive of all crops ie rice, wheat,maiz,etc...mainly 131 million food grain in 1978-79 produced in india
Rams
Punjab and haryana was the first 2 states which have been successfully adopted hyv's and due to this adoption these two states find more successfull in india and it contributed though our national income and also to GDP growth this helps in development of our nation.
Madhu

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Source:  OpenStax, Principles of economics. OpenStax CNX. Sep 19, 2014 Download for free at http://legacy.cnx.org/content/col11613/1.11
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