KIYOSHI KIMURA does not like to lose. For the past six years he has outbid all comers for the first bluefin tuna of the year sold by Tokyo’s famed Tsukiji fish market. Last week Mr Kimura, who owns a chain of sushi shops, paid ¥74.2m ($642,000) to win the first fish. That nets out to some $3,000 per kilogram.

Folk wisdom has it that high tuna-auction prices signal future economic buoyancy. Mr Kimura has said that he pays the exorbitant prices to “encourage Japan”. But that rationale seems fishy.

After a rival Hong Kong bidder baited him, Mr Kimura paid three times as much for the Tsukiji tuna in 2013 as in the previous year—a record-high ¥155.4m. GDP growth did not replicate that rise, however, sinking from 1.7% to 1.4%. In fact, Japan’s economic fortunes and Tokyo’s season-opening tuna prices seem to float rather erratically (see chart). A deep dive by The Economist suggests that tuna prices explain only 6% of the fluctuation in GDP. The correlation is a red herring.

Environmentalists, meanwhile, are gutted. Bluefin tuna are endangered; stocks have plunged by 97% from their peak, according to one estimate. The...Continue reading