What Is a Bull Market? Definition, History, and How to Invest During One

The most powerful force in investing is a sustained bull market — yet most investors either miss the early move or give back gains by selling too soon.

A bull market is more than a good stretch. It is the long, grinding, wealth-compounding period that separates investors who accumulate generational wealth from those who stay permanently cautious waiting for a pullback that turns into a two-year wait. Understanding what a bull market is, what causes it, and how to position through each of its phases is the single most valuable framework for any long-term investor.

What Is a Bull Market? The Official Definition

The most widely used definition: a bull market is a sustained rise of 20% or more in a broad stock market index from its most recent closing low. For US equities, the S&P 500 is the benchmark index used to make this determination.

The 20% threshold matters because it separates normal market volatility and short-term bounces ("bear market rallies") from genuine structural uptrends backed by improving fundamentals.

A secondary, informal definition simply describes any prolonged period of broad investor optimism and rising prices — but the 20%-from-recent-lows definition is the one market historians, strategists, and financial media use consistently.

The name originates from the way a bull attacks — thrusting its horns upward, symbolizing rising prices. Its counterpart, the bear, swipes its claws downward.

Every Bull Market Since 1950: The Data

The table below captures every major S&P 500 bull market since 1950, the starting conditions, and the total returns. This data transforms the abstract idea of "bull markets are good" into something concrete: they are long, they produce enormous wealth, and they start when most investors are still afraid to buy.

Key takeaways from the data:

• The longest bull market in history ran from March 2009 to February 2020 — 131 months, producing a 401% total return on the S&P 500
• Bull markets start before the economic recovery is visible — the March 2009 bull began while unemployment was still rising toward 10%
• Even the shorter bull markets (1966–1968, 1987–1990) produced 48–65% gains
• Missing the first 12 months of a bull market typically means missing 30–50% of the entire cycle's gains

What Causes a Bull Market?

Bull markets don't emerge from a single catalyst. They are driven by a convergence of improving conditions that collectively restore and then amplify investor confidence. The most important drivers:

1. Falling or Low Interest Rates

This is the single most powerful catalyst for bull markets. When interest rates fall:

• The discount rate applied to future corporate earnings falls → the present value of those earnings rises → P/E multiples expand
• Bond yields become less competitive vs. equities → money flows from bonds to stocks
• Borrowing costs for businesses fall → profit margins improve
• Consumer borrowing (mortgages, auto loans, credit) becomes cheaper → consumer spending rises

The 2009–2020 bull market was substantially powered by the Federal Reserve holding rates near zero (ZIRP) for seven consecutive years. The 2022–present bull market began as the Fed signaled a pause in rate hikes and markets began pricing in eventual rate cuts.

2. Strong or Improving Corporate Earnings

Bull markets cannot be sustained without earnings growth. Markets can run ahead of earnings for a period (P/E expansion), but at some point, profits must follow to justify valuations.

The earnings growth underpinning of each major bull market:

• 1982–1987: Reagan tax cuts, deregulation, oil price collapse — margins expanded dramatically
• 1990–2000: Technology productivity revolution → non-inflationary economic expansion → profit margins hit records
• 2009–2020: Post-crisis cost-cutting → lean corporate structures → record margins on modest revenue growth

3. Economic Expansion

GDP growth, declining unemployment, rising consumer confidence, and healthy credit conditions all support bull markets. Notably, bull markets lead economic cycles by 6–12 months — stocks bottom before the recession ends and peak before the expansion tops out.

4. Investor Psychology and Momentum

Once a bull market is established, momentum becomes self-reinforcing. Rising prices attract more buyers. Rising prices confirm the optimistic narrative. Rising prices cause fear of missing out (FOMO). This psychological fuel is what drives the later stages of a bull market well beyond what fundamentals alone would justify.

The Four Phases of a Bull Market

Every sustained bull market passes through recognizable psychological phases. Understanding where you are in the cycle affects how aggressively you should lean into the move.

Phase 1: Disbelief (The Wall of Worry)

The bull market begins, but almost nobody believes it is real. The prior bear market is fresh in memory. News headlines remain pessimistic. Economic data is still weak (unemployment may still be rising). Most investors who sold at the bottom wait for a "re-test of the lows" that never comes. This phase produces the best risk-adjusted returns — but the fewest participants.

Key characteristics: P/E multiples are below historical averages. Short interest is high. Retail investor sentiment surveys show excess pessimism. The market is climbing while pundits predict a reversal.

Phase 2: Acceptance

Evidence accumulates that the economy is recovering. Corporate earnings revisions turn positive. The financial media begins acknowledging the bull market is "real." Institutional investors who missed the initial move begin allocating. Valuations are roughly fair. This phase represents the "meat" of the bull market — most of the total gain is captured by long-term investors who simply held through Phase 1.

Key characteristics: P/E multiples near historical average. Earnings estimates rising. Market breadth improving — more stocks participating in the uptrend.

Phase 3: Enthusiasm

The bull market is now well-established and universally recognized. Economic data is consistently strong. Corporate guidance is optimistic. IPO markets heat up. Retail investors pour money into equities. Financial media coverage becomes relentlessly bullish. This phase is profitable but requires tighter risk management because valuations are expanding above historical norms.

Key characteristics: P/E multiples above average. High IPO and M&A activity. Narrative-driven speculation in hot sectors. Retail inflows accelerate.

Phase 4: Euphoria

The danger zone. Valuations are stretched. Speculative assets (low-quality IPOs, meme stocks, cryptocurrency, non-earning growth companies) attract enormous capital flows. "This time is different" thinking becomes widespread. Leverage in the financial system increases. The bull market can remain in this phase for months or even years (1998–2000, 2020–2021), but it ends with a correction of 20%+ that begins the next bear cycle.

Key characteristics: P/E multiples significantly above historical norms. Widespread retail speculation. Leverage-driven buying. Perma-bull narrative domination.

Sector Leadership Through the Bull Market Cycle

Not all sectors perform equally through a bull market. Leadership rotates as the economic cycle advances and as investor risk appetite evolves.

Why this rotation matters: Investors who buy defensive sectors (utilities, consumer staples) in a Phase 1 bull market will underperform significantly. The sectors that feel safest at the bottom of a bear market are typically the worst performers in the early bull market. Rotating correctly — into cyclicals early and maintaining exposure to growth leaders through the middle phases — produces substantially better outcomes than a static allocation.

Use the Stock Alarm Pro screener to filter by sector, trend state, and relative strength to identify which sectors are currently leading the bull market and find the strongest individual names within those sectors.

How Bull Markets Feel vs. How They Look in Hindsight

One of the most important — and most underappreciated — aspects of bull markets is how different they feel in real time vs. how smooth they look on a chart years later. Every major bull market included:

• Multiple corrections of 10–20% along the way (at least 5–8 per average bull market)
• Periods of 3–6 months where markets went nowhere or declined
• Major geopolitical or economic "wall of worry" events that seemed like the end
• Persistent mainstream financial media commentary that the market was "overvalued" or "due for a crash"

The 2009–2020 bull market included: the European sovereign debt crisis (2010–2011, -22% correction), the "taper tantrum" (2013, -6%), the energy sector collapse (2015–2016, -15%), and trade war anxiety (2018, -20%). Every one of these was reported as a potential bull market ender. None were.

The practical lesson: Bull market corrections are normal and healthy. They reset sentiment, reduce leverage, and shake out weak hands. Selling after a 10% correction to wait for a better entry is almost always the wrong decision in a confirmed bull market.

How to Invest During a Bull Market

Knowing a bull market exists is only valuable if you have a strategy for how to invest in it. The following approaches are ordered from most to least aggressive, mapped to investor risk tolerance and time horizon.

Strategy 1: Stay Fully Invested in a Diversified Portfolio (Everyone)

The simplest and most reliably effective strategy: maintain your target asset allocation and rebalance annually. Historical data consistently shows that investors who remain fully invested through bull markets outperform those who try to actively time entries and exits.

The opportunity cost of missing the best days: According to JPMorgan research, if an investor missed the 10 best trading days of the S&P 500 over a 20-year period (2004–2023), their total return fell from 9.7% annualized to 5.5% annualized. Missing just the 30 best days produced an annualized return of only 1.4%.

Strategy 2: Overweight Growth and Cyclical Sectors (Active Investors)

If you are willing to tilt your portfolio away from a market-cap-weighted index:

• Overweight technology, consumer discretionary, financials, and industrials in the early-to-middle phases
• Reduce utilities, consumer staples, and other defensive weightings
• Add small-cap exposure — small caps historically outperform large caps early in bull markets due to higher operating leverage

Strategy 3: Ride Momentum Leaders (Tactical Traders)

In a bull market, the strongest stocks tend to keep getting stronger. William O'Neil's CANSLIM system — which identifies stocks with strong earnings growth, new highs, and strong relative strength — was specifically designed to capture bull market leaders.

Characteristics of bull market leadership stocks:

• Within 5% of 52-week highs
• Relative strength rating above 80 (outperforming 80%+ of all stocks over the past 12 months)
• Accelerating earnings growth for 2+ consecutive quarters
• Institutional accumulation (rising volume on up days vs. down days)

Set up a screener filter combining these criteria and monitor the resulting candidates with price and volume alerts.

Strategy 4: Let Winners Run (Discipline)

The most common mistake investors make in a bull market is selling winners too early. This mistake is driven by the psychological tendency to "lock in gains" — but in a multi-year bull market, cutting a 30% winner means missing a potential 200% gain.

A better approach: use a trailing stop methodology. Instead of selling when a stock is up a fixed percentage, sell only when the stock falls a specific amount below its recent high. This lets you capture extended moves while protecting against a genuine breakdown.

For example:

• In a Phase 2 bull market: set a 15% trailing stop (normal volatility is wide)
• In a Phase 3 bull market: tighten to a 10% trailing stop as the cycle matures
• In Phase 4: use a 7% trailing stop or an alert set at the rising 50-day moving average

Set up trailing alerts on your holdings in Stock Alarm Pro →

Common Bull Market Mistakes

Even experienced investors make predictable errors in bull markets. Avoiding these protects both your gains and your ability to compound through multiple cycles.

Mistake 1: Waiting for the pullback that never comes. The most common way investors miss bull markets. Every 5% pullback seems like "the right time to buy," but the next one never arrives because the market is trending steadily upward. Studies show that waiting for a 10% correction to deploy cash in a bull market means missing 80%+ of the eventual move before that correction occurs.

Mistake 2: Selling too soon based on valuation. Valuation is a poor short-term market timing tool. Expensive markets can stay expensive for years in a bull market (the S&P 500 P/E was above 25x from 1997 to 2001 — investors who sold because "stocks were expensive" in 1997 missed 3 more years of 20%+ annual returns).

Mistake 3: Overconcentrating in last cycle's losers. After a bear market, investors naturally focus on beaten-down stocks that "should" rebound. But new bull market leaders are almost always different from the prior cycle's leaders. The Internet-era leaders (Cisco, Intel) never returned to their 2000 highs. New bull market leaders (Apple, Google, Meta) emerged from different parts of the market.

Mistake 4: Ignoring portfolio monitoring. In a bull market, the danger is complacency — not watching positions that have extended far beyond their fundamentals. Setting price and volume alerts on your holdings ensures you get notified when a stock is running too far ahead of fundamentals or when a position starts showing distribution (heavy selling on high volume).

Bull Market vs. Bear Market: Key Differences

The asymmetry matters: bull markets are longer and more powerful than bear markets. Over the past 95 years, the S&P 500 has been in a bull market roughly 75% of the time. This is why the default investment strategy — long-term buy and hold in quality equities — has outperformed almost every active strategy over time.

How to Identify a Bull Market in Real Time

Investors in Phase 1 of a bull market face a challenge: the move begins before the evidence is clear. Here are the leading indicators that a new bull market has likely begun:

1. Price crosses above the 200-day moving average — the most widely watched trend filter. When the S&P 500 crosses above its 200-day MA and the MA begins sloping upward, institutional trend-following systems shift to buy mode.

2. Market breadth expands — the percentage of S&P 500 stocks above their 200-day MA rises above 50%, indicating the rally is broad-based, not driven by 5 mega-cap stocks. The NYSE advance-decline line making new highs is a confirming signal.

3. VIX falls below 20 and continues declining — the CBOE Volatility Index measures fear. When it falls from panic levels (above 30) to complacency (below 20), risk appetite is recovering.

4. Cyclical sectors start outperforming defensives — watch the ratio of XLY (consumer discretionary ETF) to XLP (consumer staples ETF). A rising ratio means investors are rotating from defensive to offensive positioning — a classic early bull market signal.

5. New 52-week highs expand — in a genuine bull market, the list of stocks making 52-week highs grows over time. A market where only a handful of mega-caps make new highs while most stocks languish is a narrow, fragile rally, not a healthy bull market.

Set alerts for each of these signals using Stock Alarm Pro to be notified when the technical evidence confirms a new bull market phase.

Track the Bull Market With Real-Time Alerts

The best bull market investors aren't the ones who predict bull markets — they're the ones who respond quickly when the evidence confirms one and then manage their positions systematically through the cycle.

Start monitoring the market's strongest stocks with Stock Alarm Pro →

Build a bull market watchlist with the screener:

• Filter for stocks in confirmed uptrends (above both 50-day and 200-day MA)
• Sort by relative strength vs. the S&P 500
• Set price alerts at breakout levels so you're notified the moment a setup triggers
• Set volume alerts to detect institutional accumulation on your watchlist stocks

Open the Stock Alarm Pro screener to find bull market leaders →

Frequently Asked Questions

What is the definition of a bull market? A bull market is officially defined as a rise of 20% or more in a broad market index (typically the S&P 500) from its most recent closing low, sustained over at least two months. The term comes from the way a bull attacks — thrusting its horns upward.

How long does the average bull market last? The average bull market since World War II has lasted approximately 4.4 years (roughly 54 months) and produced average gains of around 152%. The longest bull market on record ran from March 2009 to February 2020 — nearly 11 years.

What causes a bull market? Bull markets are typically driven by a combination of strong or improving corporate earnings, low or falling interest rates, economic expansion, low unemployment, and improving investor sentiment. They often begin while the economy is still recovering from a recession — markets lead economic cycles by 6–12 months.

What sectors perform best in a bull market? Early bull markets favor cyclical, high-beta sectors: technology, consumer discretionary, financials, and industrials. As the bull market matures, leadership often broadens to include materials and energy. Defensives (utilities, consumer staples, healthcare) typically lag early in the cycle but may outperform late in the bull market.

How do I know if we are in a bull market right now? Check whether the S&P 500 is trading more than 20% above its most recent bear market closing low, and whether the 200-day moving average is rising and being respected as support. Market breadth — specifically the percentage of S&P 500 stocks above their 200-day MA — can confirm whether the rally has broad participation.

Disclaimer: This article is for educational purposes only and does not constitute investment advice. All investing involves risk, including the possible loss of principal. Past market performance is not indicative of future results. Always conduct your own research before making investment decisions.