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Market participants are all the parties that buy and sell in financial markets. No single classification is used everywhere; the diagram below shows how some sources sort them: Each branch is one way of sorting. By purpose, the exchange operator Intercontinental Exchange (ICE) divides derivatives traders into three groups: hedgers trade to reduce the risk of price moves, speculators open positions on their own view, and arbitrageurs seek to profit from price gaps between products. By role, the US derivatives regulator CFTC divides them into the sell side (the banks and dealers that sell financial products to clients) and the buy side (those clients themselves). And the US securities regulator SEC distinguishes retail customers from institutional investors such as funds, banks and insurers. The three ways of sorting do not exclude one another: a hedge fund is at once an institution, part of the buy side and possibly a speculator.

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How big is each group?

Once you know the names of the groups, the next question is how much of the market each one holds. The two charts below answer it for two large markets. The US stock chart rests on the Federal Reserve’s statistics on who holds the 123.7 trillion USD of US stocks at the end of Q2 2026, and the forex chart on the survey of the Bank for International Settlements (BIS) on the 9.5 trillion USD traded in foreign exchange each day in April 2025.
In US stocks, households are the largest holders: 52,119 billion of 123,687 billion USD, or 42.1%. That figure is not only individuals, because the Fed counts private equity funds and personal trusts in households and counts unlisted stocks and foreign stocks held by Americans in the total. Holding a lot of stock does not mean trading a lot, though. According to the US securities industry association SIFMA, retail investors accounted for only 17.9% of US stock trading volume in 2024. The forex market tilts toward institutions even more: 46.7% of the value traded is dealers trading with each other, while the part that comes from retail clients is only 2.5%.

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Who is long and who is short the S&P 500?

The two charts above show who is in the market but not who stands on the buying side and who on the selling side. For futures that data exists: every week the CFTC publishes the positions of each group of traders. The chart below is the E-mini S&P 500 contract on CME, as of Tuesday, September 29, 2026. The group with the largest long position is the asset managers, the pension funds, mutual funds and insurers: they are net long 1,104,434 − 200,431 = 904,003 contracts. On the other side, dealers are net short 606,988 contracts and leveraged funds (mostly hedge funds) net short 372,489. The net positions of the five groups always add up to 0, because every open contract has a buyer and a seller. From the chart you might think dealers and hedge funds are betting that the S&P 500 will fall, but that is not necessarily so. According to the CFTC, dealers often use futures to offset the risk from products they have sold to clients, and leveraged funds may be arbitraging between markets. The CFTC also notes that it classifies traders by their main activity, not trade by trade, so you cannot be sure that every position of a hedge fund is speculative.

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Who are you trading with?

Each buy order of yours trades only when someone is willing to sell, and the other way round. Who that is depends on the market you trade.
US stocks trade on order books: each exchange such as NYSE or Nasdaq matches the orders of its members in its own book. The SEC lists 29 registered stock exchanges as of January 2026, many of them belonging to the same group, such as NYSE, Nasdaq or Cboe. But exchanges are not the only place. According to the exchange operator Cboe Global Markets, 50.6% of US stock volume traded off exchange in 2025, more than half for the first time. Which of the three routes below your order takes is decided by your broker, unless you choose the venue yourself.

Exchange

The order goes into the order book of NYSE, Nasdaq or another exchange and trades against the opposite order of any member: a fund, a bank, a market maker.

ATS

An alternative trading system matches orders like an exchange but need not register as one. The order trades against orders of other parties using that system.

Wholesaler

The broker sends the order to an off-exchange dealer that specializes in retail orders, and the dealer itself buys from or sells to you.
For retail investors, the third route is the most common. Take Robinhood, a US retail broker, as an example: Rule 606 requires every US broker to publish each quarter where it sent its clients’ orders. The chart below comes from Robinhood’s Q2 2026 report, counting S&P 500 stock orders in April 2026.The top five firms received 95.18% of orders, and all five are wholesalers, not exchanges. Each broker splits differently: at Fidelity in the same month, 64.72% of S&P 500 stock orders went to wholesalers, 16.30% to exchanges and 14.29% to Fidelity’s own ATS. Even so, the overall picture leans toward wholesalers: according to the SEC in 2022, more than 90% of retail investors’ marketable orders in the US went to a small group of wholesalers, which usually fill them internally. So even though US stocks have order books, the seller to you is usually a wholesaler, not another investor on an exchange.

Brokers

What a broker does, how it is paid and where it sends its clients’ orders.

Exchanges and OTC markets

Exchanges, off-exchange trading, and which products trade where.
Last modified on October 16, 2026