Not all graphs give information about the past: some give estimated figures of future data. For example:
This graph shows the population of the United Kingdom from the year 2005 to the year 2050 measured at five year intervals. But the only figure which we can be sure about is the one for 2005 (59.9 million). All the other figures are in the future and they are estimates (what we, or the population statisticians, think the population will be). These estimates are called projections. So we can say that the UK population is projected to rise to just under 65 million in 2035. In 2040 it is estimated to remain at just under 65 million, after which it is projected to decline.
You can see that it is important to look at the axes in order to decide whether the data in the graph is a projection or not.
Sometimes projected data is indicated by a dotted or dashed line, as in the following example:
Here we can see that the population of Denmark is projected to rise to 5.5 million in 2010, after which it is projected to remain stable.
Describing Bar Charts and Column Charts (2)
Bar charts and column charts are often used to make multiple comparisons.
Observe the following chart :
It shows the populations of major European countries in the years 1996 and 2007. In this case we can make two sets of comparisons. We can look at the change in population from 1996 to 2007 for each country, and we can compare the populations of the various countries in each year.
Look at the Y axis. You can see that it starts at 30, not zero. Sometimes charts are formatted like this in order to make the differences more obvious. To see a comparison, see the next page.
In general, when describing a chart of this type, you should describe the most important change first. Then you can compare individual items (in this case, countries).
The most important information on this chart is that in all countries, except Poland, the population increased from 1996 to 2007.
Now you can compare individual countries and you can compare two things: You can compare sizes of populations and you can compare the change in populations from 1996 to 2007. We'll concentrate on the change in population.
You can compare the largest change and the smallest change: The largest change was in Turkey, where the population rose from about 62 to about 73 million, whereas the smallest increase was in Germany where the population of nearly 82 million rose by half a million. Spain also had a fairly large increase from 39.4 million to 44.5 million.
It is important to mention any exceptions to the changes you describe. In this case, the exception is Poland where the population fell very slightly in the period described.
To write a short description of this graph ask yourself (and answer!) the following questions:
- What exactly does the chart show? (Use the chart title to help you answer this question)
- What are the axes and what are the units?
- What changes are there?
- What similarities are there?
- Is it possible to put some of the columns into one or more groups?
- What exceptions are there?
Answering these questions will help you to write a short description of this simple column chart. For example:
This chart shows the populations of major European countries in 1996 and 2007. In all countries except Poland the population rose in this period. The largest rise was in Turkey where the population increased from over 62 to over 73 million, whereas the smallest increase was in Germany where the population of 82 million rose by a few thousand. Spain also had a fairly large increase from 39.4 million to 44.5 million, and France was not far behind with an increase of almost 4 million. In the other two countries, Italy and the United Kingdom, population growth was more modest with increases of about 2.3 and 2.8 million respectively. In Poland, the population fell by half a million. Poland had the smallest population in both 1996 and 2007. Although Spain and Portugal had comparable populations in 1996, Spain's population is now nearly six and a half million greater than Poland's.
You can see that where there is a change over time, you need to use some of the vocabulary used to describe line graphs (rose, increased, decreased, etc).
For comparing and contrasting, you need the vocabulary of comparison