Loosemore–Hanby index

The Loosemore–Hanby index measures disproportionality of electoral systems. It computes the absolute difference between votes cast and seats obtained using the formula:

$LH={\frac {\sum _{i=1}^{n}|\omega _{i}-\sigma _{i}|}{2}}$

The index is named after John Loosemore and Victor J. Hanby, who first published the formula in 1971 in a paper entitled "The Theoretical Limits of Maximum Distortion: Some Analytic Expressions for Electoral Systems". Along with Douglas W. Rae's, the formula is one of the two most cited disproportionality indices. Whereas the Rae index measures the average deviation, the Loosemore–Hanby index measures the total deviation. Michael Gallagher used least squares to develop the Gallagher index, which takes a middle ground between the Rae and Loosemore–Hanby indices.

Further reading

• Loosemore, John; Hanby, Victor J. (October 1971). "The Theoretical Limits of Maximum Distortion: Some Analytic Expressions for Electoral Systems". British Journal of Political Science. 1 (4). Cambridge University Press: 467–477. JSTOR 193346.

References

Works cited

• Cortona, Pietro Grilli di; Manzi, Cecilia; Pennisi, Aline; Ricca, Federica; Simeone, Bruno (1999). Evaluation and Optimization of Electoral Systems. SIAM. ISBN 978-0-89871-422-7. {{cite book}}: Invalid |ref=harv (help)
• Grofman, Bernard (1999). Elections in Japan, Korea, and Taiwan Under the Single Non-transferable Vote: The Comparative Study of an Embedded Institution. University of Michigan Press. ISBN 0-472-10909-X. {{cite book}}: Invalid |ref=harv (help)
• Lijphart, Arend; Grofman, Bernard (2007). The Evolution of Electoral and Party Systems in the Nordic Countries. Algora Publishing. ISBN 978-0-87586-168-5. {{cite book}}: Invalid |ref=harv (help)