Same votes, different rules

• The UK: First past the post. 650 single-member seats: the biggest party in each wins. Here: the cube law (seats in proportion to the cube of the vote).
• Canada: First past the post. Single-member ridings, as in the UK. Here: the cube law.
• Australia: Preferential vote. Single-member seats won with half the votes after preferences. Here: the cube law, which preferences soften in practice.
• France: Two rounds. Single-member seats, a run-off where no one wins half. Here: the cube law.
• Germany: Proportional, 5% threshold. Seats in proportion to the party vote (Sainte-Laguë) for parties with 5% or more.
• The Netherlands: Pure proportional. One national list vote: seats in proportion (D'Hondt), no threshold beyond one seat's worth.
• Poland: Proportional in 41 districts. D'Hondt in 41 districts with a 5% national threshold; mid-sized districts favour bigger parties.
• Spain: Proportional in 52 small districts. D'Hondt in 52 provinces of about seven seats, 3% threshold; small districts favour the biggest parties strongly.
• Italy: Majority bonus. A party with 42% or more takes 70 extra seats per 400, up to 55% of the chamber; the rest proportional with a 3% threshold.

Each is applied to the national vote shares shown (parties grouped as "others" left out), with France's own number of seats. These are stand-ins: real single-member and district systems depend on where each party's votes are, and voters and parties would behave differently under other rules. Read it as the same votes counted another way, not a forecast. "Our forecast" is France under its real rules. There, the grey seats (16) go to parties outside the vote shares shown; under the other rules their votes are left out, so their seats are shared among the parties shown.