TONA
The Tokyo Overnight Average Rate is Japan's overnight risk-free reference rate, published by the Bank of Japan from uncollateralized overnight call market transactions.
How it is compiled
TONA is transaction-based rather than submission-based: it summarises what was actually borrowed and lent overnight in the uncollateralized call market, rather than what a panel says it would pay. It has a single overnight tenor, which is what makes it the natural benchmark against which term rates such as TIBOR are read.
The Bank of Japan publishes a provisional fixing on the same business day and a final fixing on the following business day. Our published analysis uses final fixings only; where a provisional figure has necessarily informed a same-week observation, we say so in the issue.
Where the official rate lives
NihonRates does not publish TONA fixings. The authoritative source is the Bank of Japan's TONA market data, where final results appear on business days around 10:00 AM JST.
A fuller methodology page is in preparation. Until then, how we derive every measurement we publish is set out in the Disclaimer, and the wider picture is on the About page.