Broker

A broker is the intermediary between you and a stock exchange. When you want to buy or sell a stock, you cannot walk up to the exchange yourself; you go through a broker, who submits your order, finds a counterparty, and executes the trade. Brokers range from full-service giants offering advice and research to bare-bones discount platforms where you place orders yourself. They make money several ways, and the way they make money shapes whether their incentives align with yours.

The broker’s role in the chain

The mechanics are simple on the surface. You tell your broker you want to buy 100 shares of Apple at the market price. Your broker routes the order to a stock exchange—the NYSE, NASDAQ, or another venue. The exchange matches your order with a seller. The trade happens in milliseconds. Settlement happens a few days later: the seller receives cash, you receive the shares.

But behind that smooth surface is a complex machinery: clearinghouses that guarantee settlement, prime brokers that finance position keeping, market makers that provide liquidity, and a pecking order of commissions and fees.

For most retail investors, these details are invisible. You place an order and it fills. But the details matter because they affect your cost.

Full-service, discount, and the spectrum between

In the 1960s and 1970s, most retail investors worked with full-service brokers—large firms like Merrill Lynch or Goldman Sachs that employed armies of brokers. These brokers would call you on the phone, suggest which stocks to buy, handle your account, and charge you a commission of 1–2% on each trade.

Full-service brokers still exist, but they have largely retreated upmarket. They now focus on high-net-worth clients and charge flat fees or a percentage of assets under management. They provide research, estate planning, tax advice, and the kind of relationship a wealthy person might value. For a retail investor, a full-service broker is now unnecessarily expensive.

Discount brokers emerged in the 1970s and 1980s (Charles Schwab was the pioneer) and undercut full-service brokers on commission. A discount broker was (and is) simpler: you make your own decisions, you pay lower commissions, and you get access to a wide universe of investments. Schwab charged maybe 0.1% per trade, a 90% discount to full-service.

Robo-advisors and zero-commission brokers (Robinhood, E-Trade, TD Ameritrade, and countless others) emerged in the 2000s and 2010s and pushed commissions to zero. This seems impossibly cheap, but these brokers have found alternative revenue: payment for order flow.

Payment for order flow: the hidden cost

This is how zero-commission brokers actually make money. When you place an order to buy 100 shares, your broker does not send it to the public exchange. Instead, they sell your order to a market maker—a firm that profits by being on both sides of trades.

Here is the arrangement: A market maker might buy your 100 shares at, say, $150.00 per share and immediately resell them to you (through your broker) at $150.02. Your broker gets paid by the market maker for this flow of orders. You get a $0 commission, but you pay the 2-cent spread and never see it as an explicit cost.

Is this a bad deal? Sometimes. If you are buying and selling small amounts frequently, a 2-cent spread is negligible. If you are a day trader or place large orders, you would be better off using a broker that executes on public exchanges (even if you pay a small commission) because your orders would interact with other retail or institutional flow, not a profit-maximizing intermediary.

But for most people, most of the time, a zero-commission broker is dramatically better than the 1–2% commissions of the old days. The spread of a few cents on small retail trades is a rounding error compared to old commissions.

The economics of execution quality

Modern financial regulation has created a requirement called “best execution,” which is supposed to ensure that your broker routes your order somewhere it will get a good price. In theory, this prevents wholesale abuse. In practice, the definition of “best execution” is loose enough that sophisticated brokers can navigate it and make large amounts from payment for order flow.

The evidence is mixed. Research has shown that payment for order flow can cost retail investors meaningful money in aggregate. But the alternative—transparent commissions—also costs money. A typical retail investor is better off with Robinhood’s zero commission plus a 2-cent spread than with a traditional broker charging 0.1% commission on both legs of a trade.

What matters in choosing a broker

For a retail investor, several practical questions matter:

Commissions. Is it zero? If not, how much? For frequent traders, even a $5 per-trade cost adds up.

Custody. Is your account insured by the SIPC (Securities Investor Protection Corporation)? It should be. SIPC covers up to $500,000 per account.

Spreads and execution. Are you getting a tight spread, or is the broker’s conflict of interest (payment for order flow) visible in wider spreads?

Features. Can you trade the assets you want (stocks, ETFs, options, bonds, etc.)? Can you set up the account type you need (IRA, 401k, brokerage)?

Reliability. Does the platform work? Are there outages? Can you reach customer service?

For most retail investors, the choice is straightforward: a major discount broker (Schwab, Fidelity, Vanguard, E-Trade) with zero commissions and solid execution is sufficient.

Market-making and market quality

One last point: brokers and market makers have made modern markets far more liquid and cheaper to trade in than they were 50 years ago. The cost of trading 1,000 shares today is a fraction of what it was decades ago. This is progress, even if the revenue model is imperfect.

See also