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Some technical indicators (e.g. Williams %R) indicate whether the market is overbought or oversold.

But this doesn't make sense.

Let me explain.

Every time a stock or commodity is bought, it is also sold. And vice versa. So how can anything ever be over-bought or over-sold?

But I'm sure I'm missing something. What is it?

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Some technical indicators (e.g. Williams %R) indicate whether the market is overbought or oversold. ...

Every time a stock or commodity is bought, it is also sold. And vice versa. So how can anything ever be over-bought or over-sold?

But I'm sure I'm missing something. What is it?

You're thinking of this as a normal purchase, but that's not really how equity markets operate.

First, just because there are shares of stock purchased, it doesn't mean that there was real investor buyer and seller demand for that instrument (at that point in time). Markets have dedicated middlemen called Market Makers, who are responsible to make sure that there is always someone to buy or sell; this ensures that all instruments have sufficient liquidity. Market Makers may decide to lower their bid on a stock based on a high number of sellers, or raise their ask for a high number of buyers.

During an investor rush to buy or sell an instrument (perhaps in response to a news release), it's possible for Market Makers to accumulate a large number of shares, without end-investors being involved on both sides of the transaction. This is one example of how instruments can be over-bought or over-sold.

Since Williams %R creates over-bought and over-sold signals based on historical averages of open / close prices, perhaps it's better to think of these terms as "over-valued" and "under-valued". Of course, there could be good reason for instruments to open or close outside their expected ranges, so Williams %R is just a tool to give you clues... not a real evaluation of the instrument's true value.

  • 'it's better to think of these terms as "over-valued" and "under-valued"' <---This – thanks_in_advance Dec 30 '13 at 12:29
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You are right that every transaction involves a seller and a buyer. The difference is the level of willingness from both parties.

Overbought and oversold, as I understand them (particularly in the context of stocks), describe prolonged price increase (overbought, people are more willing to buy than sell, driving price up) and price decrease (oversold, people are more willing to sell than buy, driving price down).

  • For a stock sale to occur, it needs a buyer and a seller. Because the system is voluntary, we have to assume that both parties are "willing" to do it. One may be more willing than the other, but who's to say which one? The seller of the rising stock may be happy about her profits, but may also be feeling bad about potentially giving away profits if the stock were to rise substantially further. And so on. – thanks_in_advance Dec 30 '13 at 10:21
  • Mike's answer has it right. I was a bit unclear. What I meant by willingness (for the sake of rounding out my answer better) was the more eager party is going to be ok to pay a little higher (or sell a little lower) than the ticker price. One thing to keep in mind is that the value of a stock is constantly changing. You are not guaranteed to sell/buy a share of stock at its ticker price. – nutella Dec 31 '13 at 7:06
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Investopedia's explanation of overbought:

  1. An asset that has experienced sharp upward movements over a very short period of time is often deemed to be overbought. Determining the degree in which an asset is overbought is very subjective and can differ between investors.

  2. Technicians use indicators such as the relative strength index, the stochastic oscillator or the money flow index to identify securities that are becoming overbought.

An overbought security is the opposite of one that is oversold.

Something to consider is the "potential buyers" and "potential sellers" of a stock. In the case of overbought, there are many more buyers that have appeared and driven the price to a point that may be seen as "unsustainably high" and thus may well come down soon if one looks at the first explanation.

For oversold, consider the flip side of this. A real life scenario here would be to consider airline tickets where a flight may be "overbooked" that could also be seen as "oversold" in that more tickets were sold than seats that are available and thus people will be bumped as not all tickets can be honored in this case. For a stock scenario of "oversold" consider how IPOs work where several buyers have to exist to buy the shares so the investment bank isn't stuck holding them which sends up the price since the amount wanted by the buyers may be more than what can be sold.


The price shifts in bringing out more of one side than the other is the point you are missing. In shifting the price up, this attracts more sellers to satisfy the buyers. However, if there is a surge of buyers that flood the market, then there could be a perception that the security is overbought in the sense that there may be few buyers left for the security and thus the price may fall in the near term. If the price is coming down, this attracts more buyers to achieve the other side. The potential part is what you don't see and I wonder if you can imagine this part of the market.

The airline example I give as an example as you don't seem to think either side of buying or selling can be overloaded. In the case of an oversold flight, there were more seats sold than available so yes it is possible. Stocks exist in finite quantities as there are only X shares of a company trading at any one time if you look into the concept of a float.

  • (1) Every time there's a buyer (more buyers), there's also a seller (more sellers), why should it be "over" only one of the two. (2) The example of airline seats is interesting. There were 30 seats, and they sold 40. It's obvious why that is oversold (even though every one was also bought). But it's difficult to see why that example should be considered relevant here. Trading in stocks and commodities is so different than selling and buying of supply-constrained, finite-quantity goods and services. – thanks_in_advance Dec 30 '13 at 6:58

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