The Social Vulnerability Index (SoVI®) is constructed using a statistical procedure called a principal components analysis. The output (factors that are generated) are then labeled and their influence on social vulnerability determined (increases or decreases). The factor scores and their directional adjustments (increases or decreases vulnerability) are then put into an additive model to generate the total score. The scores are then mapped using standard deviations from the mean, normally using either 3 or 5 classes.