The Sainte-Laguë index (SLI) measures an election’s disproportionality, the adherence to the one person, one vote principle of equal representation.
Michael Gallagher stated that the Sainte-Laguë index (SLI) constructed from and minimized by the Sainte-Laguë method is "at the theoretical level is probably the soundest of all the measures.
"[1] The Sainte-Laguë index is closely related to the Pearson's chi-squared test, which some[who?]
[citation needed] The Sainte-Laguë index, as other proportionality indices, is used in psephology to compare the proportionality between various elections from various electoral systems and countries.
[3] The relationship among Sainte-Laguë index and the other indices varies depending if the election disproportionality affects smaller or larger parties more.