Sekihairitsu (惜敗率, literally the "narrow loss ratio", sometimes translated as "ratio of margin of defeat", "best loser calculation" or "second-chance rule"[nb 1]) is a method used in the proportional representation (PR) constituencies ("blocks") for the Japanese House of Representatives to determine the order of candidates placed on the same list position by their party.
After all district winners are struck from the list—as they already have won a seat and thus cannot be elected by PR—all remaining candidates put on the same list rank are then arranged according to their sekihairitsu in descending order.
While the sekihairitsu system allows – depending on a party's nomination strategy and electoral success – more successful candidates (those "narrowly losing" their districts) prioritized election by PR, it does not change the fact that the Japanese voting system is a parallel, i.e. non-compensatory voting system: The number of PR seats for a party is independent from the results in the single-member districts and is exclusively determined by the number of PR votes the party receives.
And unlike the Open list proportional voting system used since 2001 in elections for the House of Councillors of Japan where voters may choose to cast a preference vote for a single PR candidate, the sekihairitsu system doesn't allow the voters to influence directly who is elected by PR.
The first two elected PR representatives were Masayoshi Yoshino (who lost to Kōichirō Gemba by 56,858 votes to 159,826) and Ken'ya Akiba.