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Query-Based Committee Selection

Itay Asher Zimet, Shiri Alouf-Heffetz, Nimrod Talmon

Abstract

Purpose: Multiwinner voting rules typically require full knowledge of voter preferences, which becomes impractical in large-scale or attention-limited settings. This paper investigates how accurately a winning committee can be approximated when voter preferences are elicited using a limited budget of structured queries. Methods: We introduce a query-based framework for multiwinner elections in which voter preferences are elicited through refinement queries over subsets of candidates under a limited budget. We analyse several cost functions that model the cognitive effort needed to answer such queries, propose axiomatic properties for evaluating them, and experimentally evaluate simple query-based committee selection rules across multiple election models. Results: Experimental results show that strategies based on recursively splitting candidate sets provide the best trade-off between elicitation cost and committee accuracy. Across several statistical models, these strategies approximate the outcome of k-Borda elections significantly more efficiently than alternative query types. Conclusion: The results demonstrate that well-designed query strategies can substantially reduce the amount of preference information required while still producing high-quality committee outcomes, suggesting that query-based elicitation is a promising approach for scalable multiwinner decision-making.

Query-Based Committee Selection

Abstract

Purpose: Multiwinner voting rules typically require full knowledge of voter preferences, which becomes impractical in large-scale or attention-limited settings. This paper investigates how accurately a winning committee can be approximated when voter preferences are elicited using a limited budget of structured queries. Methods: We introduce a query-based framework for multiwinner elections in which voter preferences are elicited through refinement queries over subsets of candidates under a limited budget. We analyse several cost functions that model the cognitive effort needed to answer such queries, propose axiomatic properties for evaluating them, and experimentally evaluate simple query-based committee selection rules across multiple election models. Results: Experimental results show that strategies based on recursively splitting candidate sets provide the best trade-off between elicitation cost and committee accuracy. Across several statistical models, these strategies approximate the outcome of k-Borda elections significantly more efficiently than alternative query types. Conclusion: The results demonstrate that well-designed query strategies can substantially reduce the amount of preference information required while still producing high-quality committee outcomes, suggesting that query-based elicitation is a promising approach for scalable multiwinner decision-making.

Paper Structure

This paper contains 33 sections, 3 theorems, 23 equations, 4 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Related Work
  3. Multiwinner Voting.
  4. Preference Elicitation Under Incomplete Information.
  5. Query-Based Elicitation.
  6. Preliminaries
  7. Multiwinner Elections
  8. Refinement Queries
  9. Cost Functions
  10. The Query Selection Problem
  11. Choosing Cost Functions
  12. Basic Cost Functions
  13. Properties of Cost Functions
  14. Empty Questions
  15. Prefix Monotonicity
  16. ...and 18 more sections

Key Result

Theorem 1

The function satisfies all the axioms mentioned above.

Figures (4)

  • Figure 1: Committee distance from k-Borda winner under various voting rules and budget constraints (avg. over 5000 IC elections).
  • Figure 2: Committee distance from k-Borda winner under various voting rules and budget constraints (avg. over 5000 two-dimensional elections).
  • Figure 3: Map of elections coloured by election family.
  • Figure 4: Map of elections coloured by performance of random.

Theorems & Definitions (30)

  • Definition 1
  • Remark 1
  • Example 1
  • Example 2
  • Definition 2
  • Example 3
  • Example 4
  • Definition 3
  • Definition 4
  • Example 5
  • ...and 20 more