Research Methodology: What Counts in the Chartwell Index
Date: 19th March 2026
The Chartwell Index is built on a structured assessment of over 3,000 membership organisations. This article outlines how organisations are evaluated, how inclusion is determined, and how the Representative Membership Economy Set supports consistent comparison across a fragmented sector.
Most analysis of membership organisations is constructed from a narrow set of examples. A small number of well-known institutes, trade bodies or networks are taken to represent the sector as a whole. This approach is understandable, but it does not reflect how the membership landscape is actually structured in practice.
Within the Chartwell Index, more than 3,000 organisations can be identified that describe themselves, in some form, as membership-based. These range from formal professional bodies with clearly defined tiers and pricing, through to looser structures where participation substitutes for membership. In practice, these organisations do not conform to a single model, and cannot be treated as if they do.
Membership organisations tend to sit within recognisable layers. Some operate as part of a Structured Membership Economy, where membership functions as a defined economic model with clear propositions, pricing and renewal dynamics. Others operate in a more networked or representative capacity, where value is derived from coordination, advocacy or shared positioning. Beyond this sits a wider group of affinity and participation models, where membership is closer to community, interest or access.
These distinctions are evident in how organisations present themselves, how they generate value, and how they retain members. They are necessary in making sense of the sector as a whole.
The Chartwell Index is constructed to account for this directly.
All identifiable organisations are included and assessed in context. None are excluded without consideration. Each is evaluated in relation to the layer it operates within, the scale at which it operates, and its role within the sector it serves.
From this broader base, a smaller group — approximately 500 organisations — is defined as the Representative Membership Economy Set. This set brings together organisations across the Structured, Networked and Affinity layers where membership operates as a sufficiently defined and stable model to support comparison on consistent terms.
Inclusion reflects both structural clarity and sector position. Organisations must present a recognisable membership construct, alongside sufficient clarity of proposition and pricing signal, and occupy a role within their sector that supports meaningful comparison.
Other organisations remain visible within the dataset but are not treated as part of this core analytical set. This includes regional bodies, chapters of wider organisations, and structures that operate more as societies, clubs or participation groups. These form part of the long tail of membership. They are relevant in understanding the breadth of the landscape, but do not meet the criteria for inclusion in core comparative analysis.
The distinction is not one of quality or relevance. It reflects the way different organisational forms behave in practice.
A chartered institute, a national trade body and a local society may all use the language of membership, but they do not generate value, retain members, or sustain pricing in the same way. Treating them as directly comparable introduces distortion, and makes it harder to interpret the patterns that do exist.
Even within the Representative Membership Economy Set, the available data is not formulated in a uniform way. Membership organisations rarely standardise how they describe their offers. Pricing may be published, partially disclosed, or only implied. Membership tiers may be explicit or require interpretation. Benefits are often described in inconsistent or overlapping terms.
This introduces ambiguity, which is handled as part of the method rather than removed. Pricing signals are captured with associated levels of confidence. Descriptive elements are normalised to support comparison, particularly in how propositions and benefits are represented, while economic values are not forced into equivalence where underlying models differ. Where a model cannot be interpreted consistently, it may be excluded from specific forms of analysis.
The careful application of methodology, as the research has progressed, has been a significant undertaking
The careful application of methodology, as the research has progressed, has been a significant undertaking, but fundamental to establishing a basis for analysis and comparison.
Organisations can be considered alongside one another without assuming they operate in the same way. Differences in structure, pricing and retention are preserved, but placed in a context where they can be interpreted rather than treated as anomalies.
The Chartwell Index is maintained in full, but not all parts of it are used in the same way. The broader dataset establishes the shape of the landscape, while the Representative Membership Economy Set defines the portion within which comparison can be made on consistent terms. That distinction is maintained throughout.