Moving Average (MA) Basics

What is a Moving Average?

A Moving Average (MA) is an indicator that averages the closing prices over a specific period and connects them with a line. For example, a 5-day moving average is calculated by adding the closing prices of the most recent 5 trading days and dividing by 5. Each day, the oldest closing price is dropped, and a new closing price is added, updating the value. This is why it's called 'moving'.

When these average values are plotted daily and connected, they form a smooth curve. Daily price fluctuations often contain noise, but averaging them out helps to smooth this noise, revealing the larger price movement, or trend. This is why moving averages are classified as trend-following indicators.

Meaning of Moving Averages by Period

In the Korean market, commonly used periods are 5, 20, 60, and 120 days. Roughly, 5 days correspond to one week of trading, 20 days to one month, 60 days to one quarter, and 120 days to six months. Shorter periods react more sensitively to price changes, causing the line to fluctuate more, while longer periods move more slowly, revealing long-term trends.

Thus, the 5-day and 20-day MAs are used to gauge short-term trading trends, the 60-day MA for medium-term supply and demand, and the 120-day MA for the long-term direction over approximately six months. In the US market, the 50-day and 200-day MAs are commonly observed. The principle of distinguishing between short-term and long-term trends remains the same, only the specific periods differ.

A Simple Moving Average (SMA) gives equal weight to all closing prices within its period, while an Exponential Moving Average (EMA) gives more weight to recent closing prices, making it more responsive. There's no definitive answer as to which is always better; the choice depends on the nature of the stock and the timeframe being analyzed.

Normal and Inverse Alignment, Support and Resistance

When moving averages are arranged from top to bottom in the order of 5-day > 20-day > 60-day > 120-day, it's called a normal alignment. This means that shorter-term averages are higher than longer-term averages, indicating that recent prices have risen compared to past prices, which suggests an uptrend. Conversely, an inverse alignment, where the order is 120-day > 60-day > 20-day > 5-day, indicates a downtrend.

Moving averages often act as support or resistance levels. In an uptrend, if the stock price pulls back to the 20-day MA and then bounces up, the 20-day MA has acted as support. In a downtrend, if the stock price hits the 60-day MA and is pushed back down, that line becomes resistance. However, this is merely a tendency, and there's no guarantee that the price will stop exactly at that level.

Golden Cross and Death Cross

A golden cross refers to a crossover where a shorter-term moving average crosses above a longer-term moving average from below. For example, if the 20-day MA crosses above the 60-day MA, it means that the recent average price has surpassed the medium-term average, which is interpreted as a signal of a bullish reversal. A death cross is the opposite: a shorter-term MA crosses below a longer-term MA from above, and this is seen as a signal of a bearish reversal.

Specifically, if the 60-day MA is relatively flat at $11,000, and the 20-day MA rises from $10,500 to $11,200, crossing the 60-day MA, a golden cross occurs. The speed of the signal varies depending on which period combination is used; for instance, a 5-day/20-day cross is for short-term trading, while a 50-day/200-day cross is for long-term trend assessment, each interpreted according to its purpose.

One important point to note is that moving averages are based on past closing prices. Therefore, crossovers are lagging signals that appear after a trend has already somewhat developed, and they do not predict market bottoms or tops in advance.

Pitfalls and Limitations

The most common pitfall is false (whipsaw) signals that occur in a sideways market. When the stock price moves up and down without a clear direction, short-term and long-term MAs cross multiple times in quick succession, with signals reversing erratically, such as a death cross immediately following a golden cross. Relying solely on crossover signals for trading when a trend is not clear can easily lead to accumulated losses.

Furthermore, because moving averages are lagging indicators, they react slowly during periods of sharp price changes. When prices drop significantly in a single day due to sudden adverse news, the average moves slowly, meaning a death cross might appear only after a substantial decline has already occurred. Therefore, in practice, moving averages are often cross-referenced with other indicators like volume analysis or RSI.

There is also no single correct answer for setting the periods. The 5-, 20-, 60-, 120-day or 50-, 200-day periods are widely used and are conventional numbers that gain significance because many participants observe them, not because they possess inherent magic. This article explains the principles for educational purposes and does not recommend specific trades.

Checkpoints

Moving averages are trend indicators that connect the average closing prices over a specific period; shorter periods are more sensitive, and longer periods are slower. A normal alignment indicates an uptrend, while an inverse alignment suggests a downtrend, and each line can also act as support or resistance.

Golden crosses (shorter-term MA crossing above longer-term MA) and death crosses (shorter-term MA crossing below longer-term MA) should be read as trend reversal signals, but remember that both are lagging signals. To compensate for false signals in sideways markets and delays during sharp price changes, it is helpful to combine them with volume and other auxiliary indicators.