5.3 Endogeneity in studies on electoral systems

• Endogeneity (endogeneity) - the error term of a statistical model is correlated with predictors.

• It is difficult to study the mechanical and psychological effects of a voting system separately; anticipated mechanical effects affect psychological factors.
• Basic variables explaining electoral disproportionality, that is, district magnitude and voting method correlate with the number of competing parties and with the voters’ preferences distribution.