question: how can a stock price change if the volume stays at 0?
comment: Depending how the price index is calculated, it can vary as people try unsuccessfully to buy or sell. The London Stock Exchange quoted price differs depending on trading activity in that share. > Price > ..... This is the last automatic trade, the last uncrossing price **or the mid-price of the best bid and offer prices available** for the security. This is not necessarily the definitive price at which you can buy or sell securities...... So say I offer to sell XYZ shares at 2.00 and you offer to buy at 1.00, no trade is going to happen and the record price is going to be 1.50. Now maybe I need the money more desperately the next day so I drop my asking price to 1.50 but you don't bite, still no trade but the quote now shows 1.25. And so on, maybe my estimation of XYZ's future profits goes up but you don't think the same, the average of bid and offer prices doesn't converge to an actual trade for a long time.
passages: VPT is interpreted in similar ways to OBV. Generally, the idea is that volume is higher on days with a price move in the dominant direction, for example in a strong uptrend more volume on up days than down days. So, when prices are going up, VPT should be going up too, and when prices make a new rally high, VPT should too. If VPT fails to go past its previous rally high then this is a negative divergence, suggesting a weak move.
  
  Section::::Similar indicators.
  
  Other price × volume indicators:
  
  BULLET::::- Money Flow Index
  
  BULLET::::- On-balance volume
  
  BULLET::::- Accumulation/distribution index
   Total volume for each day is assigned a positive or negative value depending on prices being higher or lower that day. A higher close results in the volume for that day to get a positive value, while a lower close results in negative value. So, when prices are going up, OBV should be going up too, and when prices make a new rally high, then OBV should too. If OBV fails to go past its previous rally high, then this is a negative divergence, suggesting a weak move.
   For example, if all shareholders were to simultaneously try to sell their shares in the open market, this would immediately create downward pressure on the price for which the share is traded unless there were an equal number of buyers willing to purchase the security at the price the sellers demand. So, sellers would have to either reduce their price or choose not to sell. Thus, the number of trades in a given period of time, commonly referred to as the "volume" is important when determining how well a company's market capitalization reflects true fair market value of the company as a whole. The higher the volume, the more the fair market value of the company is likely to be reflected by its market capitalization.
   Dysart's theory, expressed in his 1967 Barron's article, was that “if volume advances and prices move up or down in accordance [with volume], the move is assumed to be a good movement - if it is sustained when the volume subsides.” In other words, after prices have moved up on positive volume days, "if prices stay up when the volume subsides for a number of days, we can say that such a move is 'good'." If the market “holds its own on negative volume days after advancing on positive volume, the market is in a strong position.”
   The average volume of a security over a longer period of time is the total amount traded in that period, divided by the length of the period. Therefore, the unit of measurement for average volume is shares per unit of time, typically per trading day.
  
  Section::::Significance.
  
  Trading volume is usually higher when the price of a security is changing. News about a company's financial status, products, or plans, whether positive or negative, will usually result in a temporary increase in the trade volume of its stock.
  
  Shifts in trade volume can make observed price movements more significant.
   Many assume Max DD Duration is the length of time between new highs during which the Max DD (magnitude) occurred. But that isn’t always the case. The Max DD duration is the longest time between peaks, period. So it could be the time when the program also had its biggest peak to valley loss (and usually is, because the program needs a long time to recover from the largest loss), but it doesn’t have to be.
  
  When "X" is Brownian motion with drift, the expected behavior of the MDD as a function of
   Higher volume for a stock is an indicator of higher liquidity in the market. For institutional investors who wish to sell a large number of shares of a certain stock, lower liquidity will force them to sell the stock slowly over a longer period of time, to avoid losses due to slippage.
  
  Section::::Legal implications.
  
  In the United States, the Rule 144 of the Securities Act of 1933 restricts the buying or selling of an amount of a security that exceed a certain fraction of its average trading volume. Therefore, the calculation of the trading volume is regulated by the SEC.
   By definition, in the long run the firm can change its scale of operations by adjusting the level of inputs that are fixed in the short run, thereby shifting the production function upward as plotted against the variable input. If fixed inputs are lumpy, adjustments to the scale of operations may be more significant than what is required to merely balance production capacity with demand. For example, you may only need to increase production by million units per year to keep up with demand, but the production equipment upgrades that are available may involve increasing productive capacity by 2 million units per year.
   This suggests that there is an optimal protection limit formula_13. If the capacity left is less than this limit demand for class 2 is rejected. If a continuous distribution formula_14 is used to model the demand, then formula_15 can be calculated using what is called "Littlewood’s rule":
  
  This gives the optimal protection limit, in terms of the division of the marginal revenue of both classes.
  
  Alternatively bid prices can be calculated via
   Volume–price trend
  
  Volume–price trend (VPT) (sometimes price–volume trend) is a technical analysis indicator intended to relate price and volume in the stock market. VPT is based on a running cumulative volume that adds or subtracts a multiple of the percentage change in share price trend and current volume, depending upon the investment's upward or downward movements.
  
  Section::::Formula.
  
  VPT total, i.e. the zero point, is arbitrary. Only the shape of the resulting indicator is used, not the actual level of the total.
   where "P" is the price, "f" is the excess demand function, and formula_2 is the speed-of-adjustment parameter that can take on any positive finite value (as it goes to infinity we approach the instantaneous-adjustment case). This dynamic equation is stable provided the derivative of "f" with respect to "P" is negative—that is, if a rise (or, fall) in the price decreases (or, increases) the extent of excess demand, as would normally be the case.
  
  If the market is analyzed in discrete time, then the dynamics are described by a difference equation such as
   That is the firm PED is 317 times as elastic as the market PED. If a firm raised its price "by one tenth of one percent demand would drop by nearly one third." if the firm raised its price by three tenths of one percent the quantity demanded would drop by nearly 100%. Three tenths of one percent marks the effective range of pricing power the firm has because any attempt to raise prices by a higher percentage will effectively reduce quantity demanded to zero.
  
  Section::::Demand management in economics.
   It is based on the concept that buying support is normally demonstrated by increased volume and repeated closes in the top half of the daily range and that selling pressure is shown by increased volume and recurrent closes in the lower half of the daily range. Rising prices typically accompany buying support and decreasing prices usually occur with selling pressure. The end result is a picture of how money is flowing into or out of a stock.
  
  To determine the CMF one must first determine the Close Location Value (CLV) as follows:
  
  formula_3 
  
  or 
  
  formula_4
   BULLET::::- Case 2: Herfindahl index = 0.80 + 5 * 0.02 + 10 * 0.01 = 0.643 (64.3%)
  
  This behavior rests in the fact that the market shares are squared prior to being summed, giving additional weight to firms with larger size.
   Some familiar valuation formulas and techniques can be understood as simplified cases of the T-model. For example, consider the case of a stock selling exactly at book value ("PB = 1") at the beginning and end of the holding period. The third term of the T-Model becomes zero, and the remaining terms simplify to:
  
  formula_26
   In the Calvo staggered contracts model, there is a constant probability h that the firm can set a new price. Thus a proportion h of firms can reset their price in any period, whilst the remaining proportion (1-h) keep their price constant. In the Calvo model, when a firm sets its price, it does not know how long the price-spell will last. Instead, the firm faces a probability distribution over possible price-spell durations. The probability that the price will last for i periods is (1-h), and the expected duration is h. For example, if h=0.25, then a quarter of firms will rest their price each period, and the expected duration for the price-spell is 4. There is no upper limit to how long price-spells may last: although the probability becomes small over time, it is always strictly positive. Unlike the Taylor model where all completed price-spells have the same length, there will at any time be a distribution of completed price-spell lengths.
   This says that the rate of change of the quantity supplied is proportional to the difference between the demand price (DP) and the supply price (SP). 
   VPT is similar to on-balance volume (OBV), but where OBV takes volume just according to whether the close was higher or lower, VPT includes how much higher or lower it was.
   Using a simplification of the above formula it is possible to estimate annualized volatility based solely on approximate observations. Suppose you notice that a market price index, which has a current value near 10,000, has moved about 100 points a day, on average, for many days. This would constitute a 1% daily movement, up or down.
   BULLET::::- A second approach to demand levelling is by deep understanding of the systems used to order products by retailers and other sellers from manufacturers. Even where this supply chain is very simple, customer-retailer-manufacturer, it is usually the case that orders are based on some form of economic order quantity (EOQ) calculation that aggregates actual customer demand over a certain period. This aggregation, and the other clever calculations that may be involved, often obscure the fact that actual demand for a product is close to flat, and for high volume products very close to flat. The demand pulsing effect is created by the ordering process and the more complex it is the greater this effect. The use of EPOS actual sales data can reveal this effect very clearly.
   BULLET::::- A third approach to demand management is to keep finished goods or nearly finished goods in stock to act as a buffer and thus isolate the production facility from actual demand. This approach is widely used today but its weakness is becoming more and more evident as a growing variety of products is demanded. The cost of making, storing, managing and protecting finished goods stock can grow to be prohibitive depending upon product range and demand variability levels. This usually means that actually whilst stocks are kept they are insufficient to meet the stated aims and so customer dissatisfaction ensues along with distressed sales (reduced price) to eliminate stock levels seen as too high.
   Besides an article he wrote for Barron's in 1967, not many of Dysart's writings are available. What can be interpreted about Dysart's NVI is that whenever it rises above a prior high, and the DJIA is trending up, a “Bull Market Signal” is given. When the NVI falls below a prior low, and the DJIA is trending down, a “Bear Market Signal” is given. The PVI is interpreted in reverse.
   The point had not been lost on Dysart, who wrote in Barron’s, “we prefer to use the issues-traded data [advances and declines] rather than the price data of any average because it is more all-encompassing, and more truly represents what’s happening in the entire market.” Dysart was a staunch proponent of using advances and declines.
  
  Fosback made three variations to NVI and PVI:
   Much like other technical indicators, The Growth X is often disputed and depends on a company's ability to continually grow earnings. If investors bid up the market value of the company faster than the earnings growth rate, then The Growth X will not form, and the relative valuation will stay flat or continue to rise. Eventually relative valuations fall as growth prospects diminish, but this can often occur quickly and cause a step function down in valuation multiples.
   At low levels of formula_4, the world is more complicated. First, most modern industrial economies experience few if any falls in prices. So the formula_45 curve is unlikely to shift down or to the right. Second, when they do suffer price cuts (as in Japan), it can lead to disastrous deflation.
  
  Section::::Debt.
  