Tree Maps

A Tool for Structuring, Exploring and Summarising Qualitative Information

Notes prepared by Rick Davies, Social Development Consultant and Research Fellow, Centre for Development Studies, Swansea, UK, 03/07/98. Email:, Fax / Phone 44 1223 841367
Please note there is a related paper at
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1. Introduction

This tool makes use of qualitative information. This information is in the form of important distinctions or difference that people see in the world around them. Important differences are those that make a difference. Differences that make a difference can be described as information (Bateson, 1979).

The term "tree map" is adapted from the field of cladistics, a methodology for the classification of living organisms into a nested hierarchy of categories based on relative commonality of structure (e.g. species, families, genera etc).

Tree maps help us deal with some problems commonly encountered when dealing with qualitative information:

  1. "The Apples and Pears" problem: How to make comparisons between complex entities. Clue: Locate the choice in a context, and bring the observer into the picture.
  2. "The Wood and Trees" problem: How to see an overall order but also to recognise local detail and diversity at the same time. Clue: Link the analysis of the macro to the micro.

2. The basic structure

A tree map is a nested classification. It can be represented as a diagram that grows from a single trunk and ends with many leaves. A simple example is given below.

treemap diagram

3. Generating a tree map

3.1 With a single respondent

Normally this method is used with one respondent. Some ways of using it with more than one person are discussed in section 3.2 below.

  1. Identify the respondent’s area of expertise or knowledge that you want to explore. For example, knowledge of animal diseases held by a paravet, or knowledge of local NGOs held by a NGO staff member working on NGO capacity building.
  2. Generate a list of actual cases which contains a wide variety of examples. For example, a list of cases treated by the paravet in the last month, or a list of NGOs known to the NGO staff member. Aim for at least twenty case and ensure there is variety. Write the name of each one down on a separate card. Cases might be events (treatment provided) or entities (clients).
  3. Place all the cards in one pile (the trunk of the tree) and ask the respondent to tell you about some of the differences between all these cases. The purpose of this question is simply to generate awareness of the large number of differences that exist.
  4. Ask the respondent to sort all the cards into two piles of any size (the first two branches above the trunk), according to what they think is the most important difference between all the cases represented on the cards. Emphasise that it is their opinion of "importance" which is important. There is no intention or requirement here to generate an "objective" description. If the project has an overall goal then the facilitator could, if they want to, refer to that goal as a general reference point, without necessarily spelling out the specifics of that goal.
  5. Emphasise that a distinction is important if it makes a difference. Because respondents may casually offer a difference simply to oblige the interviewer it is important to check its significance by asking "What difference does this difference make ?" If one can’t be identified suggest to the respondent they consider if there are other differences which might be more important.
  6. Write down a description of the reported difference at points B&C. Take each pile at B&C in turn and repeat stage 4 above. Repeat this process with all piles until there is only one example left in each pile. These become the leaves of the Tree Map
  7. In some cases there may be more than one example left in a pile but the respondent may not be able to identify an important difference between them. Don’t force them to do so, but simply note that no further difference could be identified. It may be useful to do all the above steps in the order of the groups of cards that the respondent feels they know most about first, and least about later.

3.2 With multiple respondents

There are at two basic alternatives: (a) working with a whole group, and (b) working within individuals and then comparing their individual tree maps.

The first group-based approach is relatively straightforward. Simply outline the process above (3.1) to the group, and let them discuss the matter before making a series of collective choices.

The second approach is more structured and thus more time consuming. There are two different options.

  1. Compare different applications of the same classification scheme (tree map)
    1. Present respondent A's tree map to a second respondent (B), with the difference labels attached to each branch, but without the names of the cases found at the end of those branches, at each leaf.
    2. Give the cards containing all the cases to respondent B.
    3. Ask them to proceed from the trunk upwards, sorting the cards according to the differences already labelled on the tree by respondent B, according to where they feel each card should go. Allow them to introduce additional cases if they feel that none of the cards on the existing set fit some of the branches.
    4. Compare the overlap of the two sets of classifications by visually and in terms of the percentage of common cases, out of the total number of cases used.

    Ideally, with two people working in the same situation and having the same responsibilities there should be a strong correlation between the two sets of classifications made on the same tree structure.

  2. Compare different interpretations of the same classification scheme (treemap)
    1. Present respondent A's tree map to a second respondent (B), without the difference labels attached to each branch, but with the names of the cases found at the end of those branches, at each leaf.
    2. Place the differences listed at each junction on the tree by respondent A onto a second set of cards.
    3. Ask them to proceed from the trunk upwards, placing the difference cards on whatever branches they think are suitable. Allow them to introduce additional differences if those already on the cards given to them don’t seem to fit.
    4. The two structures can then be compared visually, and in terms of the percentage of common differences, out of the total number of distinctions used.

Some progress has been made within the field of cladistics in enabling statistical comparisons of similarity between different tree maps.

3.2. Using Tree Maps

3.2.1 General uses

Value can be obtained from Tree Maps at two stages:(a) during the creation of the Tree Maps, and (b) through comparisons made between parts of the structure once it has been created.

1. During creation of a Tree Map the main use is as a enthographic tool: understanding people's view of the world. There are two forms of usage:

2. After creation there are two other types of usage. One is based on proceeding from trunk to leaf, the other is based on proceeding from leaf to trunk.

Success overall can be defined in two ways. At any one junction it will be in terms of which of the two types that exist there (as represented by particular cases). The types take on a wider generality and relevance the closer they are to the trunk. When viewed in terms of particular cases (examples) success could be seen in terms similar to a tennis tournament. The number of grades of success or performance would equal the number of junctions along a branch from trunk to leaf. In the diagram above there are three, beyond the original leaf itself. Comparisons would need to take into account the fact that some branches may be longer than others.

3.2.2 Specific Applications

  1. Assessing the impact of capacity building activities: When supporting capacity building work with individuals or whole organisations, we might expect that this assistance, either in the short or long term, would make a difference to the person or organisations relationships with their clients. One attribute of that relationship is responsiveness. The service provider might be more sensitive to the differences between client’s needs. They may also be more up to date in their knowledge about their various clients' needs. The important differences they see between their clients (that they think are important) may be more reflective of their clients concerns, and not just their own. Much of this information is available, in the first instance, in the form of knowledge the service provider has (or does not have) about its clients. This knowledge is in effect a proxy indicator. Tree maps are a way of mapping a service provider's knowledge of their clients. How differentiated is their map of the differences between clients, how up to date is their knowledge of each "leaf" and branch? How much do the descriptions of difference reflect client versus provider concerns? This information can be verified by independent observation and follow-up contacts with clients. Are services visibly differentiated (rather than homogenous)? How frequently have they been modified? Do clients views on relative value of services provided correlate with those of the provider?

  2. It should be possible to use Tree Maps as a means of doing a stakeholder analysis in a development project. This could initially be from the perspective from one observer, possibly an individual stakeholder. Firstly, a list of cases reflecting the maximum possible variety of stakeholders would be identified. The process would then start at the trunk, with the respondent identifying "the most important distinction between all the stakeholders in the project". Then each initial category of stakeholder could be progressively differentiated until all cases were located as a leaf of their own. Alternately the analysis could be attempted without prior naming of specific cases, and then differentiated to the degree of detail that was required.

  3. An alternate process would make use of multiple participants, involved on a rolling basis. The first respondent, (possibly the one person seen as the most important) would be asked to identify the first branch in the tree. People identified as most representative of each of those two branches (possibly by the first respondent) would then be asked to identify the next two branches (x2), from their point of view. People representative each of those branches (x2) would then be asked to identify the next two branches (x4), etc. Some branches may join back together again, when the same person is identified as a representative of an important sub-group by two different branches of the tree that has been developed. This should not be a problem. It makes the tree more heterarchical than hierarchical, and provides more flexibility of interpretations when, and if, experiences is aggregated back down the tree structure to the trunk

  4. Scenario planning: This is a practice widely associated with Shell. It involves developing a number of alternate views of the future and then identifying how the organisation concerned would react differently to each different scenario. Tree maps of different scenarios could be developed by starting off with a question: "What is the most important difference in views within this organisation about what it should be doing over the next 10 years ?". Within each new branch created by the answer, the question could be repeated, but pre-phrased in terms of "Within this view of the future...". Once the Tree Map is constructed a planning based set of questions could be pursued, as described above. As above, both individual and group based versions of this exercise could be designed.

  5. Qualitative monitoring: A staff member of an NGO may be working with many groups or villages. Their categorisation of these groups or villages can be documented using the tree map method. This structure then provides a framework within which comparisons can be made by that person between the different items of news they may have heard from each of these locations. News is defined here as a form of difference, a change from the previous condition. News from two sources on immediately adjacent branches can be compared in terms of its relative importance, as seen by the observer (the NGO staff member who owns the classification). The most important news (thus defined) can then be compared to the most important news from the next most adjacent branches. Complex information can be managed by making one-at-a-time comparisons. Comparisons will start at a very local level (adjacent leaves) and move to towards more global comparisons (branches next to the trunk). In organisations the organogram itself can form a similar type of tree structure and be used for the same purpose. A participatory monitoring system involving a large number of staff, designed on the this basis is described in a paper available at Another related system is described at

An Invitation

If you are interested in using this tool in any setting I would be happy to provide informal advice and comment. For further information or permission to reproduce this paper email Rick Davies at

"Dear Rick

...The information I collected through M&E news before I came away has been very useful - good case studies and ideas.

In particular I thought I would let you know that I have tried your tree map method for the first time. Despite thinking it sounded rather unlikely to be useful when I first read it, it has provided a very nice alternative to classic wealth ranking for investigating the structure of villages. The people I am working with had the same unease as I do about launching into wealth analysis. We therefore tried your method as it seemed to offer a way round the problem. We ask the number of families in the village, then ask about differences between them with respect to livestock and well-being. Following the process as you describe, we rapidly get a good idea of the wealth structure of villages, which is far more disparate than I had imagined. From this exercise it is possible to find people to interview in more detail from each category. Repeating the exercise with paravets, we then asked them to indicate what proportion of their work was with which group. This worked well and provided an indication of who was benefiting most from the services of the programme." Stephen Blakeway, Vetwork UK, at, 17 December 1998.


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