  Elections employ various voting systems to determine winners based on voters'
preferences. However, many recent ranked-choice elections have forced voters to
truncate their ballots by only ranking a subset of the candidates. This study
analyzes how forced ballot truncation affects the Bucklin, Coombs, plurality
with runoff, and Schulze voting systems' abilities to output their true winning
sets. Using computer simulations, thousands of preference profiles were
generated with the Mallows model using different numbers of candidates, voters,
and dispersion values. The true winning set was determined for each system
using complete preferences, then compared to winning sets derived from
repeatedly truncated preferences within the same preference profile. Results
show that plurality with runoff was the most resistant to forced truncation,
followed by Schulze, Bucklin, and Coombs. Additionally, elections with fewer
voters and higher dispersion values were found to decrease the probability of
selecting the true winning set across all systems. The findings provide
insights into how forced truncation impacts voting systems, aiding election
designers in their work.
