The INFORM model is based on risk concepts published in scientific literature and envisages three dimensions of risk: hazards & exposure, vulnerability and lack of coping capacity dimensions. They are conceptualized in a counterbalancing relationship: the risk of what (natural and human hazard), and the risk to what (population). 

The INFORM model balances two major forces: the hazard & exposure dimension on one side, and the vulnerability and the lack of coping capacity dimensions on the other side. Hazard dependent factors are treated in the hazard & exposure dimension, while hazard independent factors are divided into two dimensions: the vulnerability dimension that considers the strength of the individuals and households relative to a crisis situation, and the lack of coping capacity dimension that considers factors of institutional strength.

The INFORM model adopts the three aspects of vulnerability reflected in the UNISDR definition. The aspects of physical exposure and physical vulnerability are integrated in the hazard & exposure dimension, the aspect of fragility of the socio-economic system becomes INFORM’s vulnerability dimension while lack of resilience to cope and recover is treated under the lack of coping capacity dimension. The split of vulnerability in three components is particularly useful for tracking the results of disaster reduction strategies over time.  Disaster risk reduction activities are often localized and address particular community-level vulnerabilities and capacities. 

The UNISDR and most of the literature express risk by: 

Risk = Hazard × Exposure × Vulnerability

In order to accommodate the INFORM methodology, where the vulnerability variable is split among three dimensions, the equation is updated to:

Risk = Hazard&Exposure ^1/3 × Vulnerability ^1/3 × Lack of coping capacity ^1/3

It is a multiplicative equation. The risk equals zero if one of the three dimensions above is zero. Theoretically, in case of tropical cyclones there is no risk if there is no likelihood of a tropical cyclone to occur or/and the hazard zone is not populated or/and if the population is not vulnerable (e.g., all people have high level of education and live in high level of health and livelihood condition as well as they can afford houses built to a high level of wind security) or/and if the resilience of the country to cope and recover is ideal.

INFORM has three dimensions: hazard & exposure, vulnerability and lack of coping capacity. 

Each dimension encompasses different categories. Categories cannot be fully captured by any individual indicator, but serve to meet the needs of humanitarian and resilience actors. We can say that the selection of categories is user-driven (for example, UNISDR may follow the institutional category index in the coping capacity dimension while UNICEF and WFP may be more interested in the category of vulnerable groups in the vulnerability dimension). Underlying factors that contribute to the ranking results can be sought down through the levels depending on how narrowly the users intend to target their interventions. Each category can be broken down into components that capture the topic and are presented with a carefully chosen set of indicators.

The model of INFORM can be split into different levels to provide a quick overview of the issues in need of targeted actions:

• Ranking level
• Concept level – dimensions
• Functional level – categories
• Component level – sets of indicators that capture the concept of each category

The theoretical framework provides the basis for component selection, which is the next crucial step in the design of the composite index. The components should be:

• relevant: justification based on the existing literature, 
• representative and robust: focused on the component to be described, proportionally responsive to the changes, they should avoid broad measures ( e.g., GDP/capita),
• transparent and conceptually clear.

Furthermore, strengths and weaknesses of the composite index also derive from the core indicators, i.e. data sets describing the chosen component. These should be:

• reliable and open-source,
• continuous, consistent, with global coverage,
• potentially scalable from national to subnational, from yearly to seasonal (monthly) scale.

A composite index is typically a compromise between a data driven and a user driven model. There are always some components which existing data cannot describe, especially if the demands for quality of data are very high. 

Hazard & Exposure

The hazard & exposure dimension reflects the probability of physical exposure associated with specific hazards. There is no risk if there is no physical exposure, no matter how severe the hazard event is. Therefore, the hazard and exposure dimensions are merged into hazard & exposure dimension. As such it represents the load that the community has to deal with when exposed to a hazard event. The dimension comprises two categories: natural hazards and human-induced hazards, aggregated with the geometric mean, where both indexes carry equal weight within the dimension.

Vulnerability

The main focus of humanitarian organizations is people, which is the element at risk contemplated in the INFORM composite index. The impact of disasters on people in terms of number of people killed, injured, and made homeless is predominantly felt in developing countries while the economic costs of disasters are concentrated in the industrialized world. The Vulnerability dimension addresses the intrinsic predispositions of an exposed population to be affected, or to be susceptible to the damaging effects of a hazard, even though the assessment is made through hazard independent indicators. So, the vulnerability dimension represents economic, political and social characteristics of the community that can be destabilized in case of a hazard event. Physical vulnerability, which is a hazard dependent characteristic, is dealt with separately in the hazard & exposure dimension. 

There are two categories aggregated through the geometric average, socio-economic vulnerability and vulnerable groups. The indicators used in each category are different in time variability and the social groups considered in each category are the target of different humanitarian organizations. If the first category refers more to the demography of a country in general, the vulnerable group category captures social groups with limited access to social and health care systems. 

Lack of Coping Capacity

For the coping capacity dimension, the question is which issues the government has addressed to increase the resilience of the society and how successful their implementation is. The coping capacity dimension measures the ability of a country to cope with disasters in terms of formal, organized activities and the effort of the country’s government as well as the existing infrastructure which contribute to the reduction of disaster risk. It is aggregated by a geometric mean of two categories: institutional and infrastructure. The difference between the categories is in the stages of the disaster management cycle that they are focusing on. If the institutional category covers the existence of DRR programmes which address mostly mitigation and preparedness/early warning phase, then the infrastructure category measures the capacity for emergency response and recovery.