Trading and Exchanges Chapter 4: Orders and Order Properties Explained Simply
Every time you tap “buy” in your brokerage app, you are sending an order. But most people have no idea there are many different kinds of orders, and each one has very different consequences for your wallet. Chapter 4 is basically a field guide to all of them.
Market Orders: Speed Over Price
A market order says: “I want to trade right now at whatever price is available.” You get speed, but you give up control over price.
Here is the catch. When you send a market buy, you pay the best asking price. When you sell, you get the best bid price. The gap between those two is the bid/ask spread. That spread is your fee for trading immediately.
Harris gives a nice example. Amy buys a bond at the ask of 102, then immediately sells at the bid of 100. She lost 2 on the round trip. Per trade, she paid half the spread for instant execution. Think of it like paying extra for same-day delivery.
Small orders are fine. But large market orders move prices. If Martha wants to buy 400 orange juice futures, she cannot buy them all at the current ask. The market runs out of sellers at that price, so she pays higher and higher prices. This is called market impact. The bigger your order, the more you push the price against yourself.
Limit Orders: Price Over Speed
A limit order is the opposite deal. You say: “I will trade, but only at this price or better.” You control your price, but you might not trade at all.
Say the market is 48.05 bid, 48.11 ask. You place a limit buy at 48.05. If the price drops to you, great. But if it rises to 48.15, your order sits there unfilled. Now you cancel and chase the price, ending up paying more than a market order would have cost.
This is the fundamental tradeoff Harris keeps coming back to. Market orders have price uncertainty: you don’t know what price you’ll get. Limit orders have execution uncertainty: you don’t know if you’ll trade at all.
Limit Orders Are Free Options (And That Matters)
Here is the most interesting idea in the chapter. Standing limit orders are basically free options you give to the market.
If you place a limit sell at 100, you are giving every other trader the right to buy from you at 100 whenever they want. That’s a call option with a strike price of 100, given away for free.
Why does anyone do this? Because limit order traders hope to get a better price in return. Instead of buying at the ask, they try to buy at the bid. The expected savings are their compensation for giving away that free option.
But this free option can hurt you. In volatile markets, someone with better information can pick off your stale limit order before you cancel it. Harris calls this adverse selection risk. Informed traders exercise your “free option” when it benefits them and ignore it otherwise. That’s why spreads widen when markets get volatile.
Stop Orders: The Safety Net That Can Slip
Stop orders confuse beginners because they sound like limit orders. They are not.
A stop order activates when price reaches your stop price. Until then, it sits there doing nothing. Say Stan buys cotton futures at 80 cents and places a stop sell at 70 cents. If cotton drops to 70, his stop triggers and becomes a market order. He sells at whatever price is available, which could be well below 70 if the market is falling fast. Want a guaranteed exit price? You need an actual options contract.
One important detail: stop orders add momentum. When prices fall, stop sells trigger and create more selling pressure. When prices rise, stop buys add buying pressure. They amplify moves in both directions. This is why regulators worry about them during crashes.
Order Properties: The Fine Print
Beyond the basic types, orders come with a bunch of additional instructions. The most important ones:
Time in force. Day orders expire at market close. Good-till-cancel (GTC) orders stay open until you cancel them or forget about them (which Harris warns you not to do). Immediate-or-cancel orders fill right now or get killed.
Quantity instructions. All-or-none means fill the entire order at once or don’t fill it at all. Useful if partial fills would mess up your strategy.
Display instructions. You can hide the true size of your order. If Michael wants to sell 90,000 shares but only shows 10,000 at a time, that’s an iceberg order. Only the tip is visible. Showing a massive sell order would scare buyers away and push the price down.
Market-not-held orders. You tell your broker: “use your judgment, and I won’t blame you if prices move while you wait.” Institutional traders use these for large orders where market impact is a real concern.
Why Any of This Matters
If you only learn one thing from this chapter, learn the tradeoff between market orders and limit orders. Market orders cost you the spread but guarantee execution. Limit orders save you money on price but might leave you watching the market run away without you.
Understanding this tradeoff is understanding where liquidity comes from. Limit orders supply it. Market orders consume it. Every market is just these two forces pushing against each other.
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