Índice de Momentum Dinâmico

O que é o Índice de Momentum Dinâmico?

O índice de momentum dinâmico é um indicador técnico usado para determinar se um ativo está sobrecomprado ou sobrevendido. Este indicador, desenvolvido por Tushar Chande e Stanley Kroll, é semelhante ao índice de força relativa (RSI). A principal diferença entre os dois é que o RSI usa um número fixo de períodos de tempo (geralmente 14) em seu cálculo, enquanto o índice de momentum dinâmico usa diferentes períodos de tempo conforme a volatilidade muda, normalmente entre cinco e 30.

O indicador pode ser usado para gerar sinais de negociação na direção da tendência enquanto um mercado está tendendo, ou também fornecerá sinais de compra e venda durante uma variação do mercado.

Neste artigo, o índice de momentum dinâmico será ocasionalmente referido como DMI por questões de brevidade, mas não deve ser confundido com o índice de movimento direcional (DMI).

A Fórmula Para o Índice de Momentum Dinâmico

How to Calculate the Dynamic Momentum Index

The dynamic momentum index uses the RSI formula, but the DMI uses a varying look back period, between 5 and 30 for each calculation of RS, whereas the RSI typically is fixed to 14. To find the lookback period required for each calculation of RS when calculating DMI, use the following steps:

1. Calculate the standard deviation of the last five closing prices.
2. Take a 10-period moving average of the standard deviation calculated in step 1. This is StdA.
3. Divide step one by step two to get Vi.
4. Calculate TD by dividing 14 by Vi. Only use integers for the result, as these are meant to represent time periods and therefore can’t be factions or decimals.
5. TD is limited to between 5 and 30. If over 30, use 30. If under 5, use 5. TD is how many periods are used in the RS calculation.
6. Calculate for RS using the number of periods dictated by TD.
7. Repeat as each period ends.

What Does the Dynamic Momentum Index Tell You?

Traders interpret the dynamic momentum index in the same manner as the RSI. Readings below 30 are considered oversold, and levels over 70 are considered overbought. The indicator oscillates between 0 and 100.

The number of time periods used in the dynamic momentum index decreases as volatility in the underlying security increases, making this indicator more responsive to changing prices than the RSI. This is particularly useful when an asset’s price moves quickly as it approaches key support or resistance levels. Because the indicator is more sensitive, traders can potentially find earlier entry and exit points than with the RSI.

The dynamic momentum index can help traders determine when a retracement is nearing its conclusion in either a trending or rangebound market.

During a ranging market, traders watch for the indicator to fall below 30, and move back above it, in order to trigger a long trade. They would then sell, when the indicator moves above 70 or approaches the top of the range. They could then short sell when the indicator crosses back below 70 assuming the range is still intact.

During an uptrend, traders can watch for the indicator to fall below 30 and rise back above in order to trigger a long trade.

During a downtrend, watch for the indicator to rise above 70 and then fall below it in order to trigger a short trade.

30 and 70 are general levels and can be altered by the trader. For example, a trader may opt to use 20 and 80 instead.

Example of How to Use the Dynamic Momentum Index

In the chart below, the circled area shows a potential trade setup in Illinois Tool Works Inc. using the dynamic momentum index and horizontal price support. As price retraced to test the previous swing low at the start of April, the indicator gave an oversold reading below 30. The trade setup was confirmed when price failed to close below the previous low, and the indicator started to rise above 30.

Traders could place a stop-loss order either below the previous swing low or below the most recent swing low to prevent a loss if the trade moves against them. (For further reading, see: How do I use the Dynamic Momentum Index for Creating a Forex Trading Strategy?)

The Difference Between the Dynamic Momentum Index and the Stochastic Oscillator

Both these indicators measure momentum, but they are doing it in different ways and will thus produce different values and trade signals. The DMI automatically adjusts the number of periods used in its calculation based on volatility. The stochastic oscillator doesn’t do this. It has a fixed lookback period. The stochastic oscillator also has a signal line which generates additional types of trade signals. A signal line could be added to the dynamic momentum index as well.

The Limitations of Using the Dynamic Momentum Index

Overbought doesn’t necessarily mean it is time to sell, nor does oversold necessarily mean it is time to buy. When prices are falling an asset can remain in oversold territory for a long time. The indicator may even move out of oversold territory, but that doesn’t mean the price will rise significantly. Similarly, with an uptrend, the price could stay overbought for a long time, and when it moves out of overbought territory that doesn’t necessarily mean the price will fall.

The indicator is looking at past price movement. It is not inherently predictive in nature.

While the indicator lags less than the RSI, there is still some lag. The price may have already run significantly before a trade signal occurs. This means that the signal may appear good on a chart, but it occurred too late for the trader to capture the bulk of the price move.

Traders are encouraged to also consider whether the asset is ranging or trending, in order to help filter trade signals. Other forms of analysis, such as price action, fundamental analysis, or other technical indicators are also recommended.