8th Grade Civics & Math Hub

Election Math: Plurality vs. Majority

Welcome to our cross-curricular Civics and Math unit! Today we are looking at the Chicago School Board races and how candidates actually win.

You might hear people say a candidate needs "50% + 1" to win. In Chicago mayoral and aldermanic races, if no one gets a 50% + 1 majority, the top two go to a runoff. But here is a plot twist: The Chicago School Board elections actually use a Plurality system!

In a plurality system, there are no runoffs. The person with the absolute most votes wins the seat immediately, even if their total vote share is only 35% or 40%. However, hitting that 50% + 1 threshold is still the "gold standard" because it proves you have a true majority mandate from your district.

How to Calculate Vote Share

To figure out if a candidate has a true majority or just a plurality, you have to calculate their vote share percentage. The math is simple:

• Step 1: Add up all the votes cast for every candidate to get the Total Votes.
• Step 2: Divide your candidate's votes by the Total Votes.
• Step 3: Multiply by 100 to get their percentage!

If their percentage is strictly greater than 50% (which means 50% of total votes plus at least 1 more vote), they achieved a majority. If it's less than 50% but still higher than everyone else, they won by plurality.