市場では誰が売買している？機関投資家と個人投資家の見かた

⚠️ この記事は日本語訳を準備中です。現在は英語版を表示しています。

Concepts

Why look at "who is buying and selling" instead of just index moves?

The index only tells you "up or down today" — it never tells you "who pushed it up, and who was selling." The money in a market is not one uniform pool of water; it is made up of several groups of participants with different identities — some command huge capital and their moves are closely watched, others are numerous but trade in small individual amounts. Recognizing these roles and watching where their money flows tells you one layer more than staring at the index: "who is driving this move."

What roles exist in a market?

Participants fall roughly into two big categories:

• Institutions (institutional investors): They trade with institutional money, command large capital, and usually move with more discipline. In Taiwan, institutions are conventionally split into three groups, collectively called the "three institutional investors":
  • Foreign investors: Overseas institutional capital — the largest group by value in the Taiwan market, and their direction is often treated as a barometer for the broader index.
  • Investment trusts: Domestic investment trust (fund) companies — relatively active traders with window-dressing cycles.
  • Dealers: Brokerages trading with their own capital, with fast-changing positions.
• Retail investors (individual investors): Ordinary people's own money. The largest group by headcount, but small in individual ticket size and prone to emotional swings.

Roles differ across countries. Some markets report "institutions vs. individuals"; others break out foreign investors, pension funds, mutual funds, and insurance; the names and the available data all differ. So when you come to a new market, ask three questions first: Which roles exist here? Which data is actually visible? Whose weight is the largest? Identify the role with the biggest weight, and you have found the direction most worth tracking in that market.

What do "net buy" and "net sell" mean?

• Net buy: A group's "buy amount exceeds its sell amount" — that is, on that day the group as a whole was a net buyer.
• Net sell: The reverse — selling exceeds buying, and the group is a net seller overall.

Adding up each day's net buys and sells over time gives you the "cumulative net buy/sell" curve: a rising line means the period leaned toward net buying, a falling line means it leaned toward net selling. Note — this line plots fund flow, and is not the same as the index's own ups and downs.

Why are retail investors often treated as a "contrarian reference"?

In the Taiwan market, retail activity is often estimated via "margin" — investors borrowing money from brokers to buy stocks. A sharp rise in margin balances means more retail investors are chasing prices with leverage. Historically and statistically, large expansions in retail margin have often appeared at stages when the market was already running hot and sentiment was optimistic, so market convention treats it as a "contrarian reference" thermometer.

This is a statistical observation — not a guarantee of price direction, and not an instruction to trade against anyone. Its value is in reminding you "how intense the price-chasing mood is right now," not in giving trading signals.

One day, several days in a row, or a longer window?

A single day of net buying may just be noise. When reading a role's direction, the same data is viewed again at different lengths:

• Single day: Who bought and who sold on the most recent day.
• N consecutive days: Whether the same role has been a "net buyer for N straight days" — is the direction persisting?
• 5/10/20 days: Stretch the window and confirm again. Only when all three lengths agree can a trend be called steady; if you see "conflicting directions" or "no clear direction," it means the big players have not reached consensus — and that fact is itself information.

In Practice: How to Read It in CTSstock

Go to the Market Trend card in the Market view and you will see five cards — foreign investors, investment trusts, dealers, retail investors, and total — each listing net buy/sell amounts for recent trading days, along with an "N consecutive days of net buying" tag and a 5/10/20-day direction panel. Expand the Market Trend detail below, and four cumulative lines plot each role's fund flow over the period together: a line trending up leans net buy, trending down leans net sell, and the labeled endpoint on the far right shows each role's current cumulative position.

Turn on the on-chart labels (CTShelp) at the bottom of the card, and the chart will mark the foreign-investor line, the retail line, and the zero axis — helping you quickly locate "where the major players are, where the contrarian reference is, and where the boundary between net buying and net selling sits."

Note: The institutional amounts on the card are approximations estimated as "lots x closing price," not actual transaction values. They are plenty for reading direction and relative size, but do not treat them as precise figures.

Common Misconceptions

• "Retail investors are buying big — just follow them": The conventional reading runs the opposite way — a sharp rise in retail margin is, by market convention, a sign of optimistic overheating and serves as a contrarian reference, not a basis for copying trades.
• "Cumulative line going up = the index will rise": The cumulative line plots a role's net fund flow, which is a separate thing from the index; the two cannot be equated.
• "If foreign investors sell, the market must fall": Foreign investors carry large weight and are worth watching, but no single role decides the whole picture — cross-check against other roles and multiple time windows.

Related Reading

• Institutional Net Buy/Sell & Sector Rotation: Reading Fund Flow
• Want to see it live? Go to the "Market Trend" card in the Market view and pick a day to compare the directions of foreign investors and retail investors.