The single most useful thing to know about the NT ratio is this: it is not a valuation signal, it is a leadership signal. Because the Nikkei 225 is weighted by share price and TOPIX by free-float market capitalization, the ratio between them rises when a small club of high-priced growth and tech stocks leads the market, and falls when banks, autos, and the broad value complex lead. Read it as a regime gauge, and it becomes one of the cheapest pieces of market intelligence in Tokyo — two free index levels and one division.
The topic tends to surface whenever the two benchmarks visibly split. On Friday, August 21, 2026, the Nikkei 225 fell 0.30% to 66,016.36 while the broad market went the other way — the TOPIX-tracking 1306 ETF, a same-session proxy for the cap-weighted index, rose 0.31%. The most conspicuous mover behind the split was Fast Retailing, long the Nikkei’s heaviest weight, which fell 3.63% that session — and a drop of that size in a stock with the index’s largest price weighting lands far harder on the price-weighted Nikkei than on cap-weighted TOPIX. Gaps like this can run for days or weeks when leadership stays narrow. That is the NT ratio in action, and the mechanics behind it are permanent features of the Japanese market. The rest of this guide is timeless.
What the NT Ratio Is and How to Compute It
The NT ratio (enu-tii bairitsu, literally the “N-over-T multiple”) is simply:
NT ratio = Nikkei 225 index level ÷ TOPIX index level
Worked method, using the last completed session: as of the August 21, 2026 close, the Nikkei stood at 66,016.36. For the denominator you need the official TOPIX close for the same session, published by JPX — do not substitute an ETF price, which embeds fees, distributions, and premium/discount and will quietly distort the ratio.
- Divide: Nikkei close ÷ official TOPIX close. That is the entire computation.
- Interpret the level against its own recent range, not against an absolute “fair value.” There is none — the two indexes have different units, so the ratio’s level is arbitrary; only its direction and extremes carry information.
- Interpret the direction: on that specific day the Nikkei fell while the broad market rose, so the ratio ticked down — a day of narrow-leadership stocks losing to the broad market.
For context, the ratio sat roughly in the low 12s for much of the 2010s and pushed toward 14–15 during growth-led rallies in the early 2020s. To the extent today’s ratio sits above those earlier ranges, it reflects an era in which a handful of very high-priced technology names have compounded far faster than the broad market. The absolute number matters less than where it sits in its trailing one- and three-year range.
Why the Two Indexes Diverge: The Mechanics
Price weighting versus free-float cap weighting
The Nikkei 225 is a price-weighted index, adjusted by per-stock “price adjustment factors” and divided by a common divisor. Stripped of the adjustments, the principle is blunt: a stock trading at ¥70,000 pulls the index roughly twenty times harder per 1% move than a stock trading at ¥3,500, regardless of how big either company actually is. TOPIX, by contrast, weights every constituent by free-float market capitalization across the broad Tokyo market, so the largest companies — not the highest share prices — dominate.
The distortion is easiest to see side by side (closing prices, August 21, 2026):
| Stock (code) | Share price (¥) | Why it matters for the spread |
|---|---|---|
| Fast Retailing (9983) | 73,510 | Historically the Nikkei’s heaviest weight — on the order of 10% before caps — a Nikkei influence far larger than its weight in cap-weighted TOPIX |
| Tokyo Electron (8035) | 54,290 | Second tier of high-priced tech names that dominate Nikkei moves |
| Advantest (6857) | 35,900 | Semiconductor-test heavyweight; large Nikkei pull, modest TOPIX weight |
| SoftBank Group (9984) | 5,255 | Large in both, but far more influential in the Nikkei than its cap warrants |
| MUFG (8306) | 3,508 | One of Japan’s largest companies; big in TOPIX, small in the Nikkei |
| Toyota (7203) | 3,132 | Japan’s largest company by market cap, yet a modest Nikkei weight — its price is ~1/23rd of Fast Retailing’s |
That last row is the whole story in one line. Toyota, the biggest company in the country, moves TOPIX far more than it moves the Nikkei; Fast Retailing, a clothing retailer, moves the Nikkei far more than it moves TOPIX. Note that Nikkei Inc. has introduced component weight caps at periodic reviews in recent years (on the order of 10%), which blunts — but does not remove — the concentration.
Sector composition follows from the weighting
Because high share prices cluster in technology, semiconductor equipment, and a few consumer names, the Nikkei behaves like a concentrated growth index. TOPIX carries proportionally more banks, insurers, autos, trading houses, and domestic-demand stocks. Two practical consequences:
- Rates: rising domestic yields tend to support bank-heavy TOPIX relative to the Nikkei. (For scale: the 10-year JGB yielded 2.854% as of August 20, 2026, per Ministry of Finance data — a world away from the zero-rate years, and a structural tailwind for the financials that TOPIX overweights.)
- FX and global tech: the Nikkei’s semiconductor and export tilt makes it more sensitive to the yen and to US tech sentiment. Yen weakness plus a US-led tech rally is the classic recipe for a rising NT ratio.
How to Chart and Track It
- Data: both index levels are free — Nikkei levels from Nikkei Indexes, TOPIX from JPX. Daily closes are sufficient; intraday NT ratios add noise, not signal.
- Construction: divide close by close, then consider overlaying a shorter and a longer moving average of the ratio — 25-day and 200-day are reasonable choices. Crosses of the ratio through its own long moving average can serve as regime markers.
- Read extremes in percentile terms: compute where today’s ratio sits in its trailing 1–3 year range. Top decile = stretched narrow leadership; bottom decile = stretched broad/value leadership. Absolute levels go stale as the ratio drifts structurally over the years — percentiles do not.
- Common mistake: comparing today’s ratio to a level from a decade ago. Index reviews, constituent changes, weight caps, and stock splits (each handled via divisor and adjustment-factor changes) shift the ratio’s baseline over long horizons. Trend and recent range, not ancient history.
What High and Low Readings Have Signaled
- Rising / high NT ratio: narrow leadership. Semiconductor-equipment names, growth stocks, and the handful of Nikkei heavyweights outperforming the broad market — often alongside a weak yen and strong global tech. It frequently coincides with foreign-investor-driven futures buying, which concentrates in Nikkei contracts.
- Falling / low NT ratio: broad leadership. Banks and financials rallying on higher rates, value and dividend strategies working, domestic and cyclical names participating widely. Corporate-governance-driven rallies in cheap, large-cap Japan tend to show up here.
- Sharp one-day drops in the ratio often mean one thing: a heavyweight-specific shock (an earnings miss at Fast Retailing or a semiconductor-equipment name) rather than any macro rotation. Always check the day’s single-stock movers before reading a regime shift into one session.
- What it does not tell you: market direction. Both indexes can fall together with the ratio rising or falling. The NT ratio ranks leadership, not risk appetite.
How Professionals Trade It: The NT Spread
The institutional expression is a futures spread on the Osaka Exchange: long NT = long Nikkei 225 futures / short TOPIX futures (betting on narrow tech leadership); short NT = the reverse (betting on banks and broad value). Contract multipliers are structural: the large Nikkei 225 future is ¥1,000 per index point and the large TOPIX future is ¥10,000 per point, with mini contracts at one-tenth of each.
The key discipline is notional matching, not one-for-one contracts. Using the August 21, 2026 Nikkei close as an illustration: one large Nikkei contract represented roughly ¥66 million of notional (66,016 × ¥1,000). Compute the TOPIX leg the same way — official index close times ¥10,000 — and size the two legs so their total notionals match. Because the per-contract notionals differ, a balanced spread needs unequal numbers of contracts on each side, with minis closing the residual. An unmatched spread is a hidden directional bet on the whole market, which defeats the purpose.
Failure modes to respect
- Rebalance events: the Nikkei’s periodic reviews, weight-cap adjustments, and constituent changes move the ratio for purely mechanical reasons. Know the review calendar before holding a spread through it.
- SQ settlement: both futures settle to a special quotation (SQ, tokubetsu seisan shisū — the settlement price computed from constituent opening prices on expiry morning). Spread legs can settle at momentarily dislocated prices; roll early if you do not want SQ risk.
- Single-stock gap risk: a long NT position is, in practice, concentrated exposure to a handful of names. One heavyweight gapping several percent on earnings moves the spread more than most macro news — exactly the Fast Retailing dynamic described in the introduction.
- Carry and margin: two futures legs mean two margin requirements and two rolls per quarter. Small mispricings between legs at roll time can eat a thin expected edge.
FAQ
Is a high NT ratio bullish or bearish?
Neither. It says the market’s gains (or smaller losses) are concentrated in high-priced growth names rather than the broad market. Historically, stretched-high readings have marked periods of narrow tech leadership that eventually mean-revert toward value and financials — but the timing is unreliable, which is why practitioners trade the spread with defined sizing rather than treating extremes as automatic reversal signals.
Where do I get the data, and is it free?
Yes. Daily Nikkei 225 closes are published by Nikkei Indexes and TOPIX closes by JPX, both free. Divide close by close in a spreadsheet. No paid feed is required unless you need intraday values, which add little for regime analysis.
Why divide the indexes instead of subtracting them?
The two indexes are on very different scales — the Nikkei is quoted in the tens of thousands of points, TOPIX in a much smaller point range — so a point difference is meaningless and drifts with the market’s level. The ratio is scale-free, which is what makes its trend and percentile rank comparable across months and years.
Can retail investors trade the NT spread?
Mechanically yes, via Nikkei 225 mini and TOPIX mini futures (or, more roughly, paired index ETFs), and the mini multipliers make notional matching easier at small size. But it is a two-legged leveraged position with roll and margin overhead — understand the failure modes above before treating it as a simple pairs trade. Nothing here is investment advice.
Sources
- JPX statistics — www.jpx.co.jp/english (TOPIX data, futures specifications, market statistics)
- Nikkei Indexes — indexes.nikkei.co.jp/en (Nikkei 225 levels, divisor, component weights, review rules)
- Ministry of Finance Japan — www.mof.go.jp/english (JGB yield data)
- Bank of Japan — www.boj.or.jp/en (monetary policy background relevant to the rates–financials channel)
Disclaimer: This is an information and analysis publication, not investment advice. See our Methodology for data sources, standards, and our corrections policy.