Understand momentum trading

What is Momentum Trading?

The Core Principle: Trend Persistence

WHY do trends persist?

Three psychological forces drive momentum:

1. Undereaction Hypothesis: Investors initially undereact to news (earnings beats, product launches). As more investors gradually recognize the significance, the price continues adjusting upward, creating a trend.

2. Herding Behavior: Once a trend forms, investors follow the crowd. Fear of missing out (FOMO) amplifies buying pressure in uptrends; panic selling amplifies downtrends.

3. Confirmation Bias: Traders see rising prices as validation, which attracts more buyers, creating a self-reinforcing loop.

HOW long do trends last? Empirically, momentum effects are strongest over 3-12 month periods. Shorter periods (days) are often noise; longer periods (>1 year) see mean reversion (prices return toward intrinsic value).

Measuring Momentum: From First Principles

WHAT makes momentum "strong"? We need to quantify rate of price change and consistency of direction.

Derivation: Rate of Change (ROC) Indicator

Let's build the simplest momentum measure from scratch.

Given: Price observations $P_0, P_1, P_2, \ldots, P_t$ over time.

Goal: Measure how much price has changed over lookback period $n$.

Step 1: The absolute change over $n$ periods is: $\Delta P = P_t - P_{t-n}$

Step 2: To make this comparable across different assets (₹100 stock vs ₹2000 stock), we normalize by the starting price: $\text{ROC}_n = \frac{P_t - P_{t-n}}{P_{t-n}} \times 100$

WHY multiply by 100? Convention—expresses momentum as a percentage.

WHY this formula works: It's the percentage return over $n$ periods. A stock with ROC(20) = +15% has risen 15% in 20 days—strong upward momentum.

Derivation: Relative Strength Index (RSI)

ROC tells us direction and magnitude, but not overbought/oversold conditions. Let's derive RSI from scratch.

Conceptual question: Over the last $n$ days, what fraction of price movements were upward vs downward?

Step 1 - Classify daily changes: For each day $i$ in the last $n$ days, compute daily change: $\text{Change}_i = P_i - P_{i-1}$

Separate into gains and losses:

• If Change$_i > 0$: Gain$_i = \text{Change}_i$, Loss$_i = 0$
• If Change$_i \leq 0$: Gain$_i = 0$, Loss$_i = |\text{Change}_i|$

Step 2 - Average the gains and losses: $\text{Avg Gain} = \frac{\sum_{i=1}^{n} \text{Gain}_i}{n}$ $\text{Avg Loss} = \frac{\sum_{i=1}^{n} \text{Loss}_i}{n}$

Step 3 - Compute Relative Strength: $\text{RS} = \frac{\text{Avg Gain}}{\text{Avg Loss}}$

WHY this ratio? RS > 1 means gains dominate; RS < 1 means losses dominate.

Step 4 - Normalize to 0-100 scale: If Avg Loss = 0 (only gains), RS = ∞, which isn't useful. We transform: $\text{RSI} = 100 - \frac{100}{1 + \text{RS}}$

WHY this transformation?

• When RS = 0(only losses): RSI = 100 - 100/(1+0) = 0
• When RS → ∞ (only gains): RSI → 100 - 0 = 100
• When RS = 1 (equal gains/losses): RSI = 100 - 100/2 = 50

Momentum Trading Strategy: Step-by-Step

Entry Signals (Going Long)

HOW do we decide when to buy?

1. Identify the trend: Price above its moving average (e.g., above 50-day MA)
2. Confirm momentum: ROC > 0 and rising, or RSI between 50-70
3. Volume confirmation: Rising prices should come with above-average volume (shows conviction)
4. Trigger: Price breaks above a recent resistance level or makes a new52-week high

WHY volume matters? Price rising on low volume = weak momentum (few buyers). Price rising on high volume = strong conviction, trend likely to continue.

Exit Signals (Managing the Position)

Momentum trading requires strict exit discipline. Trends don't last forever.

Exit scenarios:

1. Profit target reached: Set based on risk-reward ratio (e.g., if risking 3%, target9% = 1:3 ratio)
2. Momentum weakens: RSI drops below 50, or ROC turns negative
3. Trend breaks: Price closes below key moving average (e.g., 20-day MA)
4. Stop-loss hit: Price falls to predetermined loss level (typically 2-5% below entry)

Position Sizing and Risk Management

WHAT percentage of capital per trade? Momentum trading has higher win rate but many small losses. Typical approach:

$\text{Position Size} = \frac{\text{Risk per Trade}}{\text{Distance to Stop-Loss}}$

Derivation:

• Let capital = ₹1,000
• Risk per trade = 1% of capital = ₹1,000
• Entry = ₹3,525, Stop = ₹3,420
• Distance to stop = ₹105

Shares to buy: $\text{Shares} = \frac{1000}{105} \approx 9.5 \rightarrow 9 \text{ shares}$

WHY this formula? If stop-loss hits, you lose exactly₹1,000 (1% of capital), regardless of entry price. This normalizes risk across all trades.

Common Momentum Indicators (Quick Reference)

WHY multiple indicators? Confirmation. One indicator might give false signals; combining2-3 reduces whipsaws.

Types of Momentum Strategies

1. Absolute Momentum (Time-Series Momentum)

WHAT: Trade a single asset based on its own past performance.

HOW: If 3-month return > 0, go long. If < 0, go to cash (or short).

WHY it works: Exploits autocorrelation in returns—positive returns tend to follow positive returns over3-12 months.

2. Relative Momentum (Cross-Sectional Momentum)

WHAT: Rank multiple assets, buy the top performers, short the bottom performers.

HOW:

1. Calculate 6-month returns for 50 stocks
2. Buy top 10, short bottom 10
3. Rebalance monthly

WHY it works: Winners continue outperforming winners; losers continue underperforming. Captures relative strength.

3. Dual Momentum (Combining Both)

WHAT: Use absolute momentum to time the market, relative momentum to select assets.

HOW:

1. Check absolute momentum: Is Nifty 50 > its 12-month MA? (If no, go to cash)
2. If yes, rank sectors by momentum, invest in top 3

WHY combine? Avoids bear markets (absolute momentum) while capturing strongest trends (relative momentum).

Momentum vs Mean Reversion

When to use which?

• Trending market (strong directional moves): Momentum works
• Sideways market (price bouncing between levels): Mean reversion works

HOW to identify market type? Average Directional Index (ADX). ADX > 25 = trending (use momentum). ADX < 20 = range-bound (use mean reversion).

When Momentum Trading Works Best

Market conditions:

• Bull markets (strong uptrends)
• High volatility (creates tradeable swings)
• News-driven environments (earnings seasons, sector rotations)

Asset classes:

• Individual stocks (more volatile than indices)
• Sector ETFs (technology, banking during rotations)
• Commodities during supercycles

WHY not always? In bear markets or sideways markets, trends are weak or non-existent. Momentum signals lead to whipsaws (false breakouts followed by quick reversals).

Key Differences from Other Styles

Momentum vs Day Trading:

• Day trading: Intraday (close all positions by EOD)
• Momentum: Hold days to weeks (ride multi-day trends)

Momentum vs Swing Trading:

• Swing: Trades both trend AND counter-trend moves (buys dips, sells rallies)
• Momentum: Only trades WITH the trend (never buys dips in downtrends)

Momentum vs Growth Investing:

• Growth investing: Buys fast-growing companies, holds years (fundamental analysis)
• Momentum: Buys rising prices, holds weeks (technical analysis)

Connections

• Technical Analysis Fundamentals - Momentum relies entirely on charts and indicators
• Market Psychology and Behavioral Finance - Explains WHY momentum exists (herding, undereaction)
• Risk Management in Trading - Stop-losses are critical for momentum strategies
• Moving Averages - Core tool for identifying trends
• Support and Resistance Levels - Entry triggers (breakouts)
• Volume Analysis - Confirms momentum strength
• Position Sizing - Prevents one bad momentum trade from destroying your account
• Backtesting Trading Strategies - Test momentum rules on historical data before live trading

#flashcards/stock-market

What is momentum trading? :: A short-to-medium term strategy that buys assets showing upward price momentum and sells assets showing downward momentum, based on the belief that trends persist due to behavioral factors like herding and undereaction to news.

Concept Map

Hinglish (regional understanding)