Voting and Power Indices
by Steven J. Wilson

In a weighted voting system, "players" may have more than one vote, and may not have equal numbers of votes. (This is common in publically-owned companies, where the number of shares a stockholder owns is their number of votes.) The number of votes needed for a measure to pass is called the "quota". Players with more votes often (but not always) have more power.

You can calculate the power of a weighted voting system on this page, obtaining results from two different power indices. Simply enter the quota, the number of votes for each player (up to 6 players), and press the Evaluate button. If your system has fewer than five players, enter zeros for the unwanted players.

Quota:
Player weights:
, , , , ,

Banzhaf
Power Index

Shapley-Shubik
Power Index