日本語は後半です。
Introduction Until now, I have primarily invested in U.S. equities, focusing on the S&P 500, and my portfolio currently shows significant unrealized gains. However, given the high valuation levels of U.S. stocks, future interest rate trends, and currency risks, I feel the need to rebalance a portion of my holdings to diversify risk and lock in some profits.
As a Japanese investor, I have a certain familiarity with the Japanese stock market. Therefore, I would like to examine the potential benefits of rebalancing from a U.S.-centric portfolio toward Japanese equities. Going forward, I also aim to deepen my knowledge of other international markets and conduct broader comparative analyses with a more global perspective.
Comparison of Key Market Indicators Below is a comparison of representative indices reflecting the average stock prices of major listed companies in both Japan and the United States. The graphs display values in both USD and JPY terms. However, it’s important to note that these figures do not account for dividends. As a result, Japanese stocks, which typically have higher dividend payout ratios, may appear to underperform based solely on price indices.
From these graphs, several points become clear:
A strong correlation exists between the markets, although this varies depending on the period.
There has been a pronounced trend of yen depreciation in recent years.
The U.S. stock market has shown relative strength compared to Japan.
Currently, my investments largely track the “yellow line” shown in the graphs. While the returns have been exceptionally strong, I’m increasingly concerned that it might be wise to rebalance before any potential market downturn.
Having reviewed the historical performance, let’s now examine other key indicators that can help us look ahead.
Price-to-Earnings Ratio (PER) and Price-to-Book Ratio (PBR)
S&P 500
PER: approx. 30×
PBR: approx. 4×
→ Significantly above historical averages, indicating that expectations for future growth are already priced in.Nikkei 225
PER: approx. 16×
PBR: approx. 1.5×
→ Around historical averages, suggesting that Japanese equities remain relatively undervalued.Dividend Yield
S&P 500
Around 1.3% → U.S. companies tend to rely heavily on share buybacks, resulting in lower dividend yields.
Nikkei 225
Around 2.0% → The proportion of high-dividend stocks has been increasing, making it easier for investors to earn income gains.
Overseas Revenue Ratio
S&P 500
Around 40% of revenue comes from overseas operations, highlighting the index’s strong global presence.
Nikkei 225
Around 50–60% of revenue comes from overseas, creating a structure that helps mitigate the impact of Japan’s declining domestic population.
Buffett Indicator (Stock Market Capitalization ÷ GDP)
S&P 500
Over 180% (at historical highs) → Indicates potential market overheating.
Nikkei 225
Around 150% → A comparatively restrained level.
When comparing these indicators, it becomes clear that while the U.S. stock market appears overvalued, Japanese equities may not serve as a perfect hedge in the event of a U.S. market crash due to their strong correlation.
That said, as someone who lives and spends in Japanese yen, it seems reasonable in this period of dollar strength and yen weakness to consider converting a portion of my U.S. dollar holdings back into yen and reallocating into the Japanese stock market, which appears relatively undervalued.
A common concern is the growth potential of the Japanese market. However, since companies in the Nikkei 225 derive 50–60% of their revenue from overseas—and this proportion continues to grow—the impact of domestic market contraction is likely to remain limited.
Conclusion Initially, I thought I might completely shift my investments from U.S. stocks to Japanese stocks. However, after comparing various factors, I realized that such a move wouldn’t be entirely rational. As a result, I decided to limit my sales of U.S. equities to only a portion of my holdings. Instead, to hedge against a potential sharp decline in U.S. stocks, I chose to purchase U.S. long-term corporate bonds as a way to reduce portfolio volatility.
Since I was rebalancing anyway, I also decided to allocate part of my portfolio to ETFs tracking the Nikkei 225. Additionally, given the likelihood of rising interest rates in Japan, I bought shares of Japanese banks to complete this round of rebalancing. (I believe that actually holding positions—even small ones—helps me stay attentive to market movements.)
As a Japanese investor, it’s difficult for me to predict the potential impact of U.S. tariffs, and frankly, it’s also hard to identify obvious asset classes to buy right now. Therefore, there’s a chance I might change my strategy again relatively soon. If that happens, I hope to share my reflections and update my approach in a future post.
(ここから日本語)
はじめに
私はこれまでS&P500を中心に米国株への投資を行っており、現状かなりの含み益が出ています。しかし、米国株のバリュエーションが高水準で推移していることや、今後の金利動向、為替リスクを考えると、ポートフォリオのリスク分散と利益確定の観点から、一部をリバランスする必要性を感じています。
日本人として多少なりとも親しみがある日本株式市場を取り上げて、米国株に偏った投資状況から日本株へのリバランスの有効性について考えたいと思います。今後は他国市場についても見識を深め、より広い視野で比較分析を行っていきたいと考えています。
代表的な指標の比較
こちらは日米両国の代表的な上場企業の株価平均の指標です。USD建てとJPY建てのグラフですが、配当は加味していないので配当性向の高い日本企業の方が低く見えている点は理解する必要があります。
このグラフからは以下のことが分かります。
時期にもよるが強い相関関係
近年の円安傾向
米国株式市場の優位
※現状私はこの黄色線に依った投資を行っており、あまりにリターンが高いことから暴落の前にリバランスをした方がよいのではないか？と不安になっている状態です。
過去の実績を概観できたところで、今後を見通すための他指標も見ていきましょう。
- 株価収益率（PER）と株価純資産倍率（PBR）
S&P500
PER：約30倍
PBR：約4倍
→ 歴史的平均を大幅に上回り、将来成長期待がすでに織り込まれている水準日経225
PER：約16倍
PBR：約1.5倍
→ 歴史的平均並みで、相対的に割安感が残る
- 配当利回り
S&P500
約1.3% → 米国株は自社株買いを多用するため、配当利回りは低い傾向
日経225
約2.0% → 高配当銘柄の比率が増加し、インカムゲインを得やすい
- 海外売上比率
S&P500
約40%前後が海外売上
グローバル展開が強み日経225
約50～60%が海外売上
国内人口減少の影響を限定的にできる構造
- バフェット指標（株式時価総額 ÷ GDP）
S&P500
約180％以上（過去最高水準） → 過熱感を示唆
日経225
約150％ → 相対的に抑制的な水準
こうして比べてみると、米国株式市場は割高感があるものの、たとえ暴落したとしても日本株式市場も相関関係が強いのでヘッジ先には向かない可能性があることが分かります。一方で私は日本円で生活をするので、このドル高、円安の局面では素直に一定ドルから円への交換を行い、相対的に割安な日本株市場へのリバランスを行うメリットはありそうです。
よく心配される市場の成長性ですが、日経２５５の企業は海外売上率が50 - 60%で、更に比率が高くなってきていることから、日本国内の市場縮小による影響は限定的と言えるはずです。
結論として
当初は米国株を完全に日本株に切り替えてもよいかと思っていたのですが、比較すると合理性がないように思えたので、米国株の売却は一部にとどめました。代わりに米国株の暴落のヘッジとしては、米国長期社債を買い入れてボラティリティの低減を目指すこととしました。
せっかくなので、一部は日経２２５に連動するETFの購入と、今後日本の金利が上がることから日本の銀行株を買い入れて今回のリバランスは完了しました。（ポジションを持つと今後の値動きを気にするようになるので、少しでも組み込むことが大事だと考えています。）
日本人としてはアメリカの関税の影響が読めず、また明らかに買うべきアセットクラスも見つけにくい状況なので、もしかしたらすぐに方針を買えてしまうかもしれません。その際は反省点とともに再度投稿できればと思っています。