About Worldmapper
Introduction
This website contains 696 maps, with associated information and PDF 'poster' file. Each map relates to a particular subject. Click on the 'Thumbnail Index' which gives thumbnail previews of the maps, 'Map Categories' which is classified to see the choice, or a new option 'A-Z Map Index', and view a map and associated information. There is also a Site Map | and Help page.
The country cartograms contain 171 maps showing a population grid for each covered territory/region projected on a cartogram. More information on the country cartograms are explained on this info page.
Coverage
The maps and data files cover 200 territories, mainly United Nation Member States plus a few others to include at least 99.95% of the world's population. For a map identifying them see the labelled territory map, and for a cartogram giving them all equal prominence see Appendix A (Areas Included). Further details about their names are given in Technical Notes for Land Area. Also shown on the maps are 62 other areas, mostly small islands, which do not have unique data but are assigned to and included in the data of the 200. For details see Appendix B (Islands Assigned to Territories).
Cartograms
The maps presented on this website are equal area cartograms, otherwise known as density-equalising maps. The cartogram re-sizes each territory according to the variable being mapped. The particular method used is one described by Michael Gastner and Mark Newman (see below for link). For further information, see About the Maps. To get a higher resolution map, click on the map image.
Michael T. Gastner and M. E. J. Newman (2004) Diffusion-based method for producing density equalizing maps Proc. Natl. Acad. Sci. USA 101, 7499-7504.
Colours and regions
The colours used on the maps group the territories into 12 geographical regions, and allow for an easier visual comparison between the maps than would otherwise be possible. The shading of each territory within a region is consistent throughout all of the maps.
You can view a labelled territory map with the territories labelled, and also a labelled regions map .
Posters and high-quality pdfs
The map page for the first 366 maps gives a link to a poster. This is a pdf file which has a higher resolution map and some extra information in a chart or table. It is also designed to be printed out.
Data files
When you choose a map to view, there are links at the bottom to download a data file giving the values used for all 200 territories, a graph (usually a cumulative frequency one) of the data, and a top 10 or 20 table (and the original data used, and its source).
It is important to note that all of the datasets that are used for the Worldmapper project contains estimates, approximations and inaccuracies. For more details see the data page.
There is also a data sources page giving details of the websites where much of the data has been obtained from.
Four 'underlying data files' that supply the data used for many of our maps have been made available on the data page
Technical notes
Each map has associated technical notes about the data and its sources. Additional information is present in the Technical Notes for the Land Area map Map. More information about the sources is in Data Sources.
Who we are
Details of the Worldmapper Team are given in 'About Us'. The organisations and others who have supported us are given in 'Credits' and details of how to contact us in 'Contact'. Copyright details are in '©'.
About the Maps
Land Area Map |
Population Map |
Worldmapper is a collection of world maps, using equal area cartograms where territories are re-sized on each map according to a particular variable.
In the map on the left the territories are proportional to their land area. In the one on the right the territories are in proportion to their population. The largest is China, bright green. The next largest is India, orange. Are you surprised by the relative sizes of Japan, purple, or of North America or Africa ? Population is just one variable. Every map is of a different variable, and the sizes of each territory are in proportion to the value of that particular variable.
Why use cartograms?
Cartograms allow you to plot an isolated variable. The map on the left shows land area, nothing else. The one on the right shows population, nothing else. Select another map on this site using Thumbnail Index or Map Categories. Does it look similar to the Land Area or Population cartograms or is it a totally different world view. The thumbnail maps in the Map Index allow quick comparisons. You may find it helpful to save separately or print out certain key maps that you want to frequently compare others with. Click on the map to get a higher resolution.
In order to make it easier see what a these cartograms are showing, we try to preserve the shapes of individual territories, and keep them adjacent to adjacent territories and sea. The sea is always the same proportion of the map and gives the cartogram shape. (Antarctica is treated as sea.) In a sense the maps are all to the same scale, and every map is comparable with any other however the data was measured. Every map shows the worldwide distribution of something, called a variable. If a particular country is larger on one map than another, it follows that it has a higher proportion of the world total of the first variable.
Identifying territories
On the labelled territory map the names of all but the smallest territories appear as you hover over them. The colour and shade for each territory is the same on every map. As far as possible, the territory shape and relative positions are also preserved. The data files give the values for every territory listed by region, and the PDF posters often have the top ten territories.
More than data
Values for 200 territories are used to create the maps. That number of figures is far too big to be able to take in at a glance. However the brain's visual processing skills are phenomenal, and presented as a picture you have no difficulty with that number. Before you look at a particular map, you usually have some ideas about the subject. Some of those ideas may be confirmed, other things may surprise you. You, not the cartographer, not the statistician, decide what is most striking about the figures.
Negative values
These cartograms can only show positive values: zero or negative and the territory is not shown. To overcome this, often a pair of maps is shown, e.g. showing net exports and net imports, or profit and loss. When this occurs, each territory only exists on one of the pair. If we mapped gross exports and gross imports, negative values would not arise. However the data is in dollars. Rich countries tend to pay more and charge more for goods, and that feature would dominate the maps. The net export and net import maps show the flow of money between territories in respect of the particular goods.
Methods
The process of creating an equal area cartogram is not a trivial one, and has occupied researchers for decades. A recent development by Mark Newman and Michael Gastner (described in their paper, Gastner and Newman 2004) has led to the creation of this website. The process is essentially one of allowing population to flow-out from high-density to lower-density areas, and they used the linear diffusion method from elementary physics to model this process. The code developed as a result of the Gastner and Newman paper has been released and is available here.
Reference
Michael T. Gastner and M. E. J. Newman (2004) Diffusion-based method for producing density equalizing maps Proc. Natl. Acad. Sci. USA 101, 7499-7504.
About the Data Files
On each page of the Worldmapper website you can access data files that contain all the data used to create each map. Most of the data files consist of three sheets, a Data sheet, a Graph sheet and an Info sheet.
The Data Sheet
Data for the world is followed by data for
Columns A, B, C and D are common to all the Data sheets. A detailed explanation of each of these columns is in the technical notes for Land Area (001).
Column A
assigns a number to each of the 200 territories. Numbers 1 to 177 are the 2004 Human Development Index rank of all the territories included in the main United Nations Development Index in 2004. Top is Norway. Numbers 178 to 200 are the other 23 territories we have used in alphabetical order.
Column B
gives the region or territory name.
Column C
gives a territory's region number. The territories are usually sorted alphabetically by region.
Column D
gives the territories ISO 3 code, or ISO ALPHA-3 code a three letter code devised by the International Organization for Standardization.
Column E
is the actual data used for the map. It allows you to be precise about what the map shows. For example, that the area of one territory is double that of another although the shapes are very different. You may be surprised at how well you can tell which is the larger of two territories by eye. If negative values of the variable are possible, these will be shown as zero because equal area cartograms cannot show negative values. Details about other columns appear in the Technical notes files for that particular map. Column F is often the rate of the variable (either per person or per land area).
A policy of Worldmapper is to always map the same 200 territories so that every map is comparable with every other one. Although most of the sources used cover most of these territories, we have usually had to use other sources or statistical methods to get the necessarily complete data set. Moreover territories vary considerably in both their ability and desire to produce accurate data, and this also varies from topic to topic. The Technical Notes, accessible from each map page, give the original sources that we have used for that map, and any particular problems we have had with the available data and with creating the data needed for mapping. Equal area cartograms require that you have appropriate data for all 200 territories that we are mapping. (If any of these territories does not appear on one of our maps, then the map implies a zero or negative value.) Consequently if data is unavailable for particular territories then various assumptions have to be made to estimate it. We hope we have created maps where inacuracies in the data used are rarely visible.
To find the exact figure used for mapping click on the relevant cell in column E of the data sheet and you will see the number in the formula bar. If this is to an impossible degree of accuracy, it may indicate a computed value. Impossibly identical figures in say column F show that we have, for want of data, assumed the two territories are similar; and used that figure to obtain one for column E. Exact figures of zero or 100% have several causes. Zero may indicate a negative value. The United Nations agency may have only requested figures from a subset of territories, assuming that everywhere else the figure is so low or so high as to be irrelevant in the global picture, and we have decided that a reasonable map can still be created. Sometimes the territory has actually given zero or 100% to the agency who have recorded it. If so, we have also accepted it, even if improbable.
For any serious use of the data, please refer back to the data sources given in the relevant Technical Notes. For any other uses, please remember that our data set has been constructed purely to create a reasonable map in which inaccuracies will be rarely visible. We make no other claim for it.
For the Expert
We are not experts on many of the subjects that we map but are aware that international data can be unsatisfactory and inadequate. By making such data more accessible, we hope to encourage the provision of good quality international data. If you have advice on how to improve it, please approach the organisation, given in the technical notes, providing our data. We would like to be told of secondary sources of data for territories where we have had to make estimates. We would also appreciate any essential comment about the data that you feel needs to be added to the technical notes. (email info@worldmapper.org)
The Graph Sheet
This sheet usually shows a graph at the top left. At the top right are tables of top and bottom ten, or top twenty for the variable which are used in the PDF files. Below appears the data used to create the graph and tables.
Most of the 200 territories shown on the graph appear as vertical black lines. Twelve territories appear coloured, one for each region: the territory in the region with the highest y value. On the Excel data file, hover over the horizontal coloured bar and the territory name will appear.
Some of the graphs show cumulative frequency. These can be a bit tricky to understand, but repay studying. If you read down the y axis you can choose any number. Read across and the graph will give you an x value. You can then state that that number of y occur in territories with less than so many x. It is not the appearance of these graphs that matters, but the ability to make those sort of statemants from it that is important.
In the bottom ten table, we have sometimes used different units from the top ten table. When this occurs the values are highlighted.
The data files below are all ordered by total population. Various figures are given for creating the graph, including ranking all 200 territories in column F.
The Info Sheet
This gives very basic information about the file.
More information
If this page doesn't answer your questions, try the FAQ page, or email info@worldmapper.org
The following pages may also be of interest:
This page was authored by David Dorling on behalf of the Worldmapper team.
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