Normalization and Aggregation

Normalization and aggregation, the essential steps for estimating any index, are outlined below. Our approach is grounded in a strong foundation provided by the policy and academic literature on composite indices. We provide a work through example using Sweden to illustrate how we normalization and aggregation data to create a score.

Normalisation

Normalization ensures that data is comparable across indicators, allowing for meaningful combination into an index. It requires all indicators to be presented in such a way that higher or lower values consistently represent better or worse performance. Consequently, we transformed some indicators to meet this requirement. A common method of normalization involves rescaling values to a range of 0 to 1 (or 0 to 100), where 0 represents the theoretically lowest performance and 1 (or 100) represents the theoretically highest score. This approach is used in various indices, such as the Migrant Integration Policy Index (Solano and Huddleston 2020), the Multiculturalism Policy Index (Multiculturalism Policy Index 2024), and the Human Development Index (United Nations Development Programme, annually since 1990). For further information on normalization click here

Aggregation

Using the normalisation approach, we created standardized indicators for each area, with scales ranging from 0 to 100. For each area, we construct, to the extent possible, both a policy and a practice subindex. Two areas, CE in teacher training and period of compulsory education, do not have a practice subindex and are thus exclusively defined by a policy subindex.

The aggregation process to arrive at the overall EfDI consisted of three stages. In the first stage, the normalized scores of the indicators were combined to form a separate practice and a separate policy subindex for each area. The second stage consisted of combining the practice and policy subindexes for each area to develop separate subindexes for the seven areas. In the final stage we combined the subindexes of the seven areas to produce the overall EfDI index. For further information on aggregation click here