TOKYO — In the single most honest act in modern finance, the Tokyo Stock Exchange announced Wednesday it is removing nearly 700 companies from its flagship Topix index, confirming what investors have suspected since the first ticker: the market is a list, and lists have custodians.

Japan Exchange Group unveiled the biggest-ever reshuffle of the Topix, a revamp that will shrink the benchmark from roughly 1,600 constituents to under 1,000 — a 40 percent haircut — by applying tougher inclusion rules to companies whose shares barely trade. The exchange’s logic is unimpeachable: if nobody is buying or selling a stock, it is not really in the market. It is just in a phone book.

The move will redirect an estimated $1 trillion in passive money. That is the beautiful part. Index funds buy whatever the index says. So when the index deletes a company, robots worldwide must sell it, and when the index adds 35 new names, the same robots must buy them, at scale, on schedule, without sentiment. The largest pool of capital on Earth is obedient to a spreadsheet. Japan simply updated the spreadsheet.

"We are not crashing these companies. We are simply observing, on the record and with a committee, that no one has purchased them since February."

The culled firms — small regional manufacturers, aging department stores, a shuttle company serving a ferry no longer runs — are not being delisted from the exchange. They are being delisted from relevance, which traders concede is the sharper of the two knives. A company inside the index is owned, in a small way, by every pension fund on the planet. A company outside the index is owned by whoever remembered it existed.

THE PURGE, BY THE NUMBERS

  • Companies earmarked for removal: 683, chosen by rules so boring they are unarguable.
  • Companies added: 35, selected for actually being traded, a criterion the old Topix had somehow survived without.
  • Passive money in motion: Roughly $1 trillion, moving because a list changed, which is all money has ever moved for.
  • Implementation: Gradual, because Japan does not believe in shocking the robots.
  • U.S. response: None. American indices remain curated by committees that refuse to say how many companies they have removed, which Americans call maturity.

Economists praise the reform with the relief of people watching a neighbor finally clean a yard everyone had agreed not to look at. An index is supposed to measure an economy. The Topix had begun measuring a filing cabinet. The fix was not a stimulus, a rate cut, or a speech. The fix was an edit.

At press time, shares of one culled company — a prefectural maker of ceremonial incense with average daily trading volume of nine shares — rose 14 percent on the news, having finally been noticed by someone.