How is the SIGI built?
The SIGI is a composite index that builds on a framework of 4 dimensions, 16 indicators and 25 underlying variables (for the fifth edition). Data collected for the SIGI cover 179 countries. Because of data gaps, SIGI scores were calculated, in 2023, for 140 countries.
The statistical methodology of the SIGI consists in aggregating the levels of discrimination as measured by the variables into 16 indicators, which are in turn aggregated into 4 dimensions. These 4 dimensions are then aggregated into the SIGI score. At each stage of the aggregation process, the same aggregation formula is used. The current methodology was developed in 2017 following an extensive process of consultation with gender and statistical experts and was first applied for the fourth edition of the SIGI published in 2019. In 2020, the methodology was assessed again during an Expert Group Meeting and an internal quality review was undertaken in 2021 with the support of OECD’s Statistics and Data Directorate. The fifth edition of the SIGI in 2023 applies this methodology for the second time.
For more information on how the SIGI methodology was developed and works, please read the SIGI Methodological Paper.
What are the underlying variables?
The SIGI 2023 builds on 26 variables that span across the 16 indicators of the framework. The index uses three types of variables:
Legal variables that describe the level of discrimination in legal frameworks. These variables are based on a legal questionnaire (the SIGI 2023 Legal Survey) of 173 questions. Questionnaires were first filled by legal experts and professional lawyers from national and international law firms, before being reviewed by the Gender team of the OECD Development Centre and sent to governments for validation. The cut-off date for the legal information collected was 31 August 2022.
Attitudinal variables that describe the level of discrimination in social norms. The cut-off date for the attitudinal data was 31 December 2022.
Practice variables that describe the level of discrimination in terms of prevalence and parity. The cut-off date for the practice data was 31 December 2022.
How are variables selected?
Attitudinal and practice variables of the SIGI 2023 were selected based on the following criteria:
Conceptual relevance: The variable should be closely related to the conceptual framework of discriminatory social institutions and measure what it is intended to capture.
Underlying factor of gender inequality: The variable should capture an underlying factor that leads to unequal outcomes for women and men.
Data quality, reliability, and coverage: The variable should be based on high-quality, reliable data. Ideally, the data should be standardised across countries/territories and have extensive coverage across countries/territories.
Distinction: Each variable should measure a distinct discriminatory institution and should add new information not measured by other variables.
Statistical association: Variables included in the same dimension should be statistically associated, and thereby capture similar areas of social institutions without being redundant.
How is legal information encoded into the legal variables?
The information captured by the SIGI 2023 Legal Survey was encoded to create 15 legal variables across each indicator of the SIGI conceptual framework – the only indicator that does not have a legal variable is the Missing women indicator as there are no laws that can be measured for this type of discrimination against girls.
A coding manual was developed to ensure consistency across variables, and guarantee objectivity in the selection criteria for scoring. A five-level classification (0, 25, 50, 75 and 100) serves as the basis to encode the legal information and reflects the level of discrimination in formal and informal laws: 0 denotes equal legal protections between women and men, without legal or customary exceptions, and 100 denotes a legal framework that fully discriminates against women’s and girls’ rights.
The scores of the legal variables take into account all applicable legal frameworks in the country whether formal or informal, including those that may only apply to part of the population. In many countries across the world, dual, plural, federal or informal legal frameworks may exist or co-exist. The SIGI methodology which takes this into account by assessing whether the law applies to all groups of women may affect the individual performance of countries.
To learn more, read the SIGI Methodological Paper.