Daily Economics, Business and Finance Study
October 8, 2026 (KST) · Day 18
Today's Topic: Moving Averages Are Not Predictions — Understanding Average Prices, Trends, Bullish Alignment and Lag
1. Review of yesterday's key points
In Day 17, we learned that a candlestick condenses a period's open, high, low and close into a Result, and that trends are judged by sequences of highs and lows across multiple periods, rather than a single candle. Today, we will study moving averages, which smooth fluctuating daily closing prices to make trends easier to see, along with their limitation: they do not predict the future.
2. Today's core concept
A moving average is a line connecting price averages recalculated each day over a specified period. The most basic simple moving average is:
\[ N\text{-day simple moving average (SMA)}_t = \frac{P_t+P_{t-1}+\cdots+P_{t-N+1}}{N} \]
Here, \(P_t\) usually denotes today's closing price, and \(N\) is the number of periods included in the average.
Today's lesson has four objectives.
- Understand how simple moving averages (SMA) and exponential moving averages (EMA) are calculated.
- Describe trend conditions using moving-average direction, alignment and distance from the price.
- Understand why golden crosses and death crosses are lagging signals by nature.
- Use moving averages to support price-structure, volume and company-value analysis, rather than as standalone buy or sell signals.
3. Concept explained
3-1. A Simple Moving Average Removes the Oldest Price and Adds the Newest
For example, a 5-day moving average adds the closing prices of the latest 5 trading days and divides by 5. The next day, the oldest closing price is removed and the newest is added before recalculating. Because the calculation window moves forward one day at a time, this is called a moving average for that reason.
For example, if the latest 5 closing prices are KRW 10,000, 10,200, 10,400, 10,300 and 10,600, the 5-day average is:
\[ \frac{10,000+10,200+10,400+10,300+10,600}{5} =10,300\text{ KRW} \]
If the next day's closing price is KRW 10,800, the first day's KRW 10,000 drops out of the calculation.
\[ \frac{10,200+10,400+10,300+10,600+10,800}{5} =10,460\text{ KRW} \]
The new closing price rose by KRW 200, but the 5-day average rose by KRW 160. A moving average blends multiple days' prices, so it moves more slowly than the daily price. Its benefit of reducing noise and its drawback of responding slowly to change arise from the same mechanism.
3-2. Shorter Periods Are More Sensitive; Longer Periods Are Smoother
Choose the moving-average period to match the time frame being analyzed.
| Category | General Characteristics | Strength | Weakness |
|---|---|---|---|
| Short-Term Moving Average | Greater weight on recent prices | Responds quickly to changes | Frequently changes direction even with small fluctuations |
| Medium-Term Moving Average | Between short and long term | Balances trend clarity and sensitivity | Lags abrupt turning points |
| Long-Term Moving Average | Averages a long price history | Smoothly displays the broader trend | Signals can be substantially delayed |
Korean daily stock charts commonly use 5-, 20-, 60- and 120-day averages, while US markets also frequently use 50- and 200-day averages. These are market conventions intended to capture roughly a week, month, quarter, half-year or approximately 1 year of trading days, rather than absolute laws.
A 20-period average means 20 trading days on a daily chart, 20 weeks on a weekly chart, and the latest 20 thirty-minute intervals on a 30-minute chart. Always check the chart's time unit, rather than the number alone.
3-3. SMA and EMA Assign Different Weights to Prices
A simple moving average (SMA) gives equal weight to every closing price in the calculation window. For a 20-day SMA, the price from 20 days ago and today's price each carry a weight of one-twentieth.
An exponential moving average (EMA) gives greater weight to recent prices. Its basic formula is:
\[ EMA_t=\alpha P_t+(1-\alpha)EMA_{t-1} \]
The usual smoothing factor is:
\[ \alpha=\frac{2}{N+1} \]
For example, for a 5-day EMA, \(\alpha\) is as follows.
\[ \alpha=\frac{2}{5+1}=\frac{1}{3}\approx33.3\% \]
If today's close is KRW 10,800 and the previous day's EMA is KRW 10,300:
\[ EMA_t =0.333\times10,800+0.667\times10,300 \approx10,467\text{ KRW} \]
An EMA responds more quickly to recent price changes than an SMA, but is correspondingly more sensitive to short-term noise. Neither method is always superior. Apply the same calculation method consistently when comparing the same stock and period.
3-4. Consider the Moving Average's Direction Alongside the Price's Position
A price above its moving average is higher than the recent average price; one below it is lower. However, judging the trend from position alone can produce errors.
| Price and Moving Average | Moving-Average Slope | Basic interpretation |
|---|---|---|
| Price above the line | Rise | A typical condition in a continuing uptrend |
| Price above the line | Fall | A sharp rebound may have occurred while the prior downtrend remains intact |
| Price below the line | Rise | May be a short-term correction within an uptrend |
| Price below the line | Fall | A typical condition in a continuing downtrend |
Thus, the following questions matter more than simply noting that the stock moved above its 20-day average.
- Is the 20-day average itself rising?
- Are prior highs and lows also moving higher?
- Did volume and a verifiable catalyst accompany the breakout?
- Did the price remain above the line at the close?
- Are the market and industry peers moving in the same direction?
Because moving averages form curves, it is more realistic to view one as a dynamic zone of average prices that market participants may watch, rather than a wall at one exact price.
3-5. Bullish and Bearish Alignment Are Results of a Trend
The ordering of multiple moving averages is called their alignment. For example, when short-, medium- and long-term averages are all rising in the following order, this is bullish alignment.
\[ \text{Price}>\text{Short-term MA}>\text{Medium-term MA}>\text{Long-term MA} \]
Conversely, falling averages in the following order are in bearish alignment.
\[ \text{Price}<\text{Short-term MA}<\text{Medium-term MA}<\text{Long-term MA} \]
Bullish alignment results from recent prices becoming higher than longer historical averages, so it displays an uptrend at a glance. Bearish alignment is the reverse.
However, by the time bullish alignment is complete, the stock may already have risen substantially. Bullish alignment is not a cause guaranteeing further gains; it describes how average prices across multiple time frames have become ordered from high to low.
If the lines are tangled and their slopes are flat, the market is likely moving sideways within a range. In such periods, prices may repeatedly cross moving averages, producing frequent false signals.
3-6. Golden Crosses and Death Crosses Confirm Trends Late
A short-term moving average crossing a long-term average from below to above is commonly called a golden cross, while a crossing from above to below is called a death cross in market terminology.
A crossover means that the average of recent prices has risen above, or fallen below, the average over a longer period. Actual prices must move first for a crossover to occur, making the signal inherently lagging.
For example, a falling stock may already have rebounded 20% before its 20-day average crosses above its 60-day average. Conversely, a death cross may appear only after a substantial decline from the peak. The delay is not purely a flaw: the approach gives up the initial move in exchange for checking whether a trend has developed to some extent.
Problems arise in sideways markets. When prices fluctuate within a range, short- and long-term averages may cross repeatedly, producing **whipsaws**: a decline immediately after a golden cross or a rebound immediately after a death cross.
When examining a crossover signal, also check:
- Whether the two moving averages slope in the same direction
- Whether the structure of highs and lows has also changed
- Whether trading volume and value have increased
- Whether earnings estimates, guidance and industry conditions have improved
- Whether relative strength is distinguishable from the overall market's rise or fall
3-7. Deviation Shows How Far Price Is from Its Average
The distance between the current price and its moving average can be expressed as a percentage.
\[ \text{Deviation rate} = \frac{\text{Current price}-\text{Moving average}}{\text{Moving average}} \times100 \]
Alternatively, current price divided by the moving average and multiplied by 100 is sometimes called the disparity index.
\[ \text{Disparity index} = \frac{\text{Current price}}{\text{Moving average}} \times100 \]
If the current share price is KRW 10,800 and the 5-day average is KRW 10,460:
\[ \text{Deviation rate} = \frac{10,800-10,460}{10,460}\times100 \approx3.25\% \]
\[ \text{Disparity index} = \frac{10,800}{10,460}\times100 \approx103.25 \]
When price moves far from its average, you can assess potential short-term overbought or oversold conditions. But a large deviation does not guarantee an immediate return to the average. With new information such as strong upward earnings revisions or structural adverse developments, the average itself may subsequently follow prices.
There is no absolute threshold for being “overheated.” Normal deviation ranges differ between volatile growth stocks and stable consumer staples, and even the same stock behaves differently around earnings releases and in ordinary periods. Historical volatility, industry characteristics and events should be considered together.
3-8. A Moving Average Is Not the Average Purchase Cost of Actual Holders
A simple moving average equally averages each period's Close. Because it does not incorporate volume, it does not show the prices and quantities at which market participants actually traded.
VWAP is a representative indicator that weights prices by volume.
\[ VWAP = \frac{\sum(\text{Price}\times\text{Volume})}{\sum \text{Volume}} \]
| Category | Moving Average | VWAP |
|---|---|---|
| Main Inputs | Closing price for each period | Price and volume |
| Weighting Method | SMA weights time periods equally | Greater weight for executions with larger volume |
| Typical Use | Identify trends across multiple periods | Compare average execution prices intraday or over a specified interval |
| Limitation | Does not incorporate volume | Depends on the chosen starting point |
A price may repeatedly rebound near a moving average, but this should not be attributed automatically to “every investor's break-even price.” Possible influences include the self-fulfilling effect of many participants placing orders around the same line, trend-following strategies and coincidental price overlap.
3-9. Different Price Adjustments and Data Bases Can Distort Long-Term Moving Averages
Corporate actions such as stock splits, reverse splits, bonus issues, rights offerings and ex-dividend adjustments can create mechanical breaks in price series. For example, after a 10-for-1 split, the share price theoretically falls to one-tenth of its prior level, but 90% of the company's value has not disappeared that day.
Leaving pre-split prices unadjusted in a long-term moving average can create a nonexistent crash and a distorted average. Check the following bases.
- Whether prices are raw or adjusted
- Whether the adjustment reflects total returns, including cash dividends
- Whether only regular-session closes or also extended-hours prices are included
- How trading-halt days and market holidays are treated
- Whether different exchanges, currencies or time zones have been mixed
Charting services may use different adjustment methods and EMA initial values, causing small differences even for the same stock and period.
4. A simple numerical example
The following are hypothetical company A's 6 hypothetical trading days of closing prices for learning are shown. Prices are in KRW.
| Trading Day | Close | 3-Day SMA on That Day | 5-Day SMA on That Day |
|---|---|---|---|
| Day 1 | 10,000 | Cannot be calculated | Cannot be calculated |
| Day 2 | 10,200 | Cannot be calculated | Cannot be calculated |
| Day 3 | 10,400 | 10,200 | Cannot be calculated |
| Day 4 | 10,300 | 10,300 | Cannot be calculated |
| Day 5 | 10,600 | 10,433.3 | 10,300 |
| Day 6 | 10,800 | 10,566.7 | 10,460 |
① The 3-Day SMA on Day 6
Use the latest 3 closing prices, from days 4–6.
\[ 3\text{-day SMA} = \frac{10,300+10,600+10,800}{3} =10,566.7\text{ KRW} \]
② The 5-Day SMA on Day 6
Use the latest 5 closing prices, from days 2–6.
\[ 5\text{-day SMA} = \frac{10,200+10,400+10,300+10,600+10,800}{5} =10,460\text{ KRW} \]
③ Alignment and Deviation Rate
On day 6, the order is:
\[ \text{Current price }10,800 > 3\text{-day MA }10,566.7 > 5\text{-day MA }10,460 \]
The short-term average is above the longer-term average, and the current price is above both, so this is close to bullish alignment in the short term. However, 6 days of data cannot establish the long-term trend.
Deviation from the 5-day average is:
\[ \frac{10,800-10,460}{10,460}\times100 \approx3.25\% \]
④ Why Does It Lag?
From day 1 to day 6, the close rose 8% from KRW 10,000 to KRW 10,800. But the 5-day average rose only approximately 1.55%, from KRW 10,300 when first calculated on day 5 to KRW 10,460 on day 6.
\[ \text{Increase in 5-day MA} = \frac{10,460-10,300}{10,300}\times100 \approx1.55\% \]
Actual prices move first; the moving average follows as older prices drop out of the calculation one by one. This example shows that moving averages organize and display trends, but do not predict the rise beforehand.
5. Practical use in equity and company analysis
① Use Moving Averages as Trend Filters
Even after company-value analysis identifies a potential purchase, the market may still be pricing in adverse information. Moving averages can serve as supplementary filters for the current price trend, rather than tools for calculating fair value.
For example, an uptrend may be considered relatively clear when these conditions appear together.
- The price is above rising medium- and long-term moving averages
- Short-, medium- and long-term averages are in bullish alignment
- Highs and lows are both rising
- Earnings estimates and guidance are being raised
- Volume increases during advances and declines during corrections
Conversely, if an apparently undervalued company keeps making lower highs and lower lows below a falling long-term average, check whether the market is still pricing in lower earnings or financial risk. A chart cannot replace company valuation, but it can warn of conflict between a fundamental hypothesis and the market price.
② Distinguish Between Time Frames
Do not mix the time frames of long-term investing and short-term trading.
| Investment Question | Example of the Primary Time Frame | Role of the Moving Average |
|---|---|---|
| Is company value growing over several years? | Monthly and weekly charts; long-term averages | Check the broader trend and potential long-term deterioration |
| Did the trend change after the earnings release? | Daily chart; medium-term averages | Assess stabilization after a gap and the repricing process |
| Are you choosing an entry point over several days? | Daily and intraday charts; short-term averages | Observe short-term overheating and pullbacks |
If the weekly chart remains in a long-term uptrend but the daily price falls below its 20-day average, this may be a short-term correction within the longer trend. Conversely, a daily golden cross while the long-term weekly average is falling sharply may indicate a rebound within a broader downtrend.
③ Do Not Buy Solely Because Price Crosses a Moving Average
When price crosses above a moving average, check in the following order.
- Price Structure: Has it also broken above the previous high?
- Direction of the Line: Has the moving average turned upward?
- Trading Participation: Have trading volume and value increased above usual levels?
- Business Evidence: Have earnings, orders, guidance or industry data improved?
- Valuation: Are improved expectations already excessively reflected in the current price?
- Invalidation Conditions: Which price or disclosure changes would lead you to revise your assessment?
This sequence helps distinguish a simple technical rebound from a repricing of company value.
④ Do Not Treat It as One Exact Line of Support or Resistance
A 20-day average at KRW 50,000 does not guarantee a rebound at KRW 50,000. Moving averages change daily, and intraday volatility can cause a temporary break below the line followed by recovery.
It is therefore better to define a zone and confirmation conditions, for example:
- Set an observation zone of ±1–2% around the 20-day average
- Distinguish intraday breaks from closing breaks
- Check whether volume increases during the break
- Check whether the price recovers quickly on the next trading day
- Check whether the prior swing low also breaks
The zone's width should reflect the stock's usual volatility. Applying a fixed 1% threshold to a highly volatile stock can generate too many unnecessary signals.
⑤ Do Not Immediately Trade Against a Large Deviation from the Average
If a stock is far above or below its moving average, assess whether a new entry's risk-reward profile has deteriorated. But do not short solely because the positive deviation is large, or buy solely because the deviation is low.
- A rise driven by earnings upgrades: the average may catch up slowly, allowing a large deviation to persist
- A fall caused by a liquidity shock: mean reversion may be possible if company value has changed little
- A fall caused by structural earnings deterioration: the historical average price may no longer be a suitable benchmark
Before expecting mean reversion, assess whether company value is intact and only the price has temporarily overshot.
⑥ Include Hidden Costs When Testing Crossover Strategies
Marking golden crosses and death crosses on historical charts can make a strategy look simple, but proper testing requires the following.
- When a trade can actually be executed if the buy or sell signal becomes known at the close
- Commissions, taxes, bid-ask spreads and market impact
- Survivorship bias from excluding delisted stocks
- Adjusted prices reflecting splits, dividends and rights offerings
- Look-ahead bias from mixing future data into historical calculations
- Overfitting by testing many periods and choosing only the one that looks best
Ignoring these costs and biases can overstate actual performance. The purpose of moving averages is not to find a perfect trading formula, but to observe complex price movements using a consistent framework.
6. What to look for in filings
Moving averages, golden crosses and deviation rates are not financial-statement items in company filings. Prices and volume should be obtained from exchange and market data, while the business developments and corporate actions behind those prices should be checked in Filing.
Korean Companies: DART and Exchange Disclosures
Financial Supervisory Service DART and Korea Exchange KIND for the following materials.
| Filing or material | Connection to Moving-Average Analysis |
|---|---|
| Annual and Quarterly Reports | Verify actual changes in revenue, operating income, cash flow and business risks |
| Preliminary Results and Earnings Disclosures | Identify the earnings catalysts behind price breakouts and trend changes |
| Supply Contracts, Investments, Acquisitions and Disposals | Verify the scale, duration and conditions of new growth expectations |
| Rights Offerings, Convertible Bonds and Bonds with Warrants | Check potential share supply and dilution risk |
| Treasury-share acquisitions and disposals | Check potential company purchases or supply to the market |
| Stock Splits, Reverse Splits, Bonus Issues and Dividends | Identify causes of mechanical adjustments to the price series |
| Disclosures on Trading Halts, Administrative Designations and Delisting | Identify price discontinuities and liquidity risk |
| Controlling-shareholder or executive ownership changes | Verify transactions by insiders and major shareholders |
If there has been a stock split or ex-rights adjustment, check how the chart adjusts historical prices. Disclosure timing also matters. Intraday disclosures may affect that day's price, while releases after the close may primarily affect the next trading day's open and moving-average calculation.
U.S. companies: SEC EDGAR
SEC EDGAR for the following documents.
- 10-K·10-Q: Actual results, risk factors, cash flow and changes in share count
- 8-K: Material events such as earnings releases, acquisitions or disposals, major contracts and restructuring
- Form 4: Insider transactions by officers and directors
- Schedule 13D·13G: Changes in major shareholders' holdings and investment intentions
- S-3·424B: Stock and convertible-security issuance and potential dilution
- 10b5-1 Disclosures: The existence of, and changes to, prearranged insider trading plans
- Stock Split and Dividend Announcements: Reasons for adjustments to prices and share counts
US stocks frequently have earnings announcements before and after the regular session and active extended-hours trading. A moving average calculated only from regular-session closes may not reflect extended-hours price changes until the following day.
Market Data Needed Beyond Company Filings
| Data | Essential Basis to Check |
|---|---|
| Daily, Weekly and Intraday OHLC | Time zone, session coverage and exchange |
| Adjusted Closing Prices | How splits, dividends and changes in shareholder rights are reflected |
| Trading volume and value | Units and whether off-exchange and extended-hours trading are included |
| SMA·EMA | Period, price input and EMA initial value |
| VWAP | Calculation start point and included trades |
| Market and Industry Indices | Compare relative performance over the same period |
| Earnings Consensus | As-of date, provider and whether estimates were recently revised |
It is useful to record the as-of date, time frame, adjustment basis and calculation method together, for example: “As of the October 8, 2026 close; daily chart; adjusted closing prices; 20-day SMA.”
7. Key takeaways
- A moving average connects price averages recalculated daily over a specified period.
- An SMA equally weights prices in its calculation window, while an EMA gives greater weight to recent prices.
- Shorter periods react faster to price changes but generate more false signals; longer periods are smoother but respond later.
- Consider not only whether price is above its moving average, but also the line's slope, the structure of highs and lows, and volume.
- Bullish and bearish alignment summarize trend conditions across time frames but do not guarantee future rises or falls.
- Golden crosses and death crosses are lagging signals that follow price moves; whipsaws are common in sideways markets.
- The deviation rate shows distance from the average, but a large deviation does not imply an immediate reversal.
- A moving average is a time average of closing prices, not actual investors' average purchase cost, and should be distinguished from the volume-weighted average price, VWAP.
- Prices that do not reflect corporate actions such as splits, dividends and share issuance can distort long-term moving averages.
- In practice, use moving averages as trend filters supporting price-structure, volume, filing and earnings analysis, rather than as a method for calculating fair value.
8. Three review questions
Question 1
Hypothetical Company B's latest 5 closing prices are KRW 20,000, 20,500, 20,300, 20,800 and 21,400. Calculate the 5-day SMA and the final closing price's percentage deviation from it.
Question 2
The 20-day average crossed above the 60-day average, creating a golden cross. Explain two reasons why this alone cannot establish that the stock will rise the next day.
Question 3
After better-than-expected earnings, Company C's price is above rising 20-day and 60-day averages, which are in bullish alignment. However, the price is 18% above the 20-day average and volume is 5 times normal. What else should you examine before considering a new purchase?
Answers and explanations
Answer 1
The 5-day SMA is:
\[ \frac{20,000+20,500+20,300+20,800+21,400}{5} =20,600\text{ KRW} \]
The final closing price's deviation rate is:
\[ \frac{21,400-20,600}{20,600}\times100 \approx3.88\% \]
The final closing price is approximately 3.88% above the 5-day average. This alone cannot establish overheating; consider the stock's usual volatility and the reasons for the rise.
Answer 2
First, moving averages are calculated from past prices, so crossovers lag an actual price increase. Second, sideways markets can produce whipsaws as the averages cross repeatedly, allowing the price to fall immediately after a golden cross. Check both lines' slopes, the structure of highs and lows, volume, earnings changes and valuation together.
Answer 3
Bullish alignment and heavy volume indicate an uptrend, but an 18% deviation above the 20-day average may imply an unfavorable risk-reward profile for chasing the price in the short term. Check the following.
- How far earnings exceeded consensus and whether forward guidance was also raised
- Whether P/E, FCF yield and DCF updated for the new results justify the current price
- Whether heavy volume marks the start of a long-term repricing or overheating mixed with short-term profit-taking
- Whether the gap and the prior breakout zone subsequently act as support
- The intended entry range during a pullback and the conditions invalidating the investment thesis
- Whether relative strength persists after accounting for the overall market and industry advance
A moving average helps confirm a candidate stock's trend; it does not automatically justify an expensive price.
Next Lesson — Day 19:
“RSI and MACD Are Recalculations of Price — The Limits of Momentum, Overbought Signals and Divergence”