The 48% Tipping Point: BofA’s Hartnett Warns Mega-IPOs Are Fueling a ‘Roaring ‘20s’ Bubble

 

 The 48% Tipping Point: BofA’s Hartnett Warns Mega-IPOs Are Fueling a ‘Roaring ‘20s’ Bubble

**Subheading:** *With SpaceX targeting a $2 trillion valuation and OpenAI racing toward a $1 trillion IPO, Bank of America’s top strategist says tech’s weight in the S&P 500 could soon surpass every major bubble in history. “Strong price action, retail mania, slumping vol… so bubbly.”*

**Estimated Read Time:** 6 minutes

**Target Keywords:** *BofA Hartnett bubble warning, SpaceX IPO valuation $2 trillion, OpenAI IPO 2026, market concentration 48% threshold, Roaring Twenties stock market, Nifty 50 1970s bubble, Japanese asset bubble 1980s, dot-com bubble 1990s.*

## Part 1: The Human Touch – The Warning from the Man Who Saw 2025 Coming

Let me tell you about a strategist who has a habit of being right—and why his latest warning is making Wall Street squirm.

It's May 22, 2026. Michael Hartnett, Bank of America's chief investment strategist, just released a note that has fund managers checking their risk limits. Hartnett is not a permabear. He correctly predicted the outperformance of international equities last year. His bullishness on commodities has paid off handsomely. When he speaks, institutional investors listen.

His latest message? **The market is flashing “bubble” signs not seen since the Roaring ‘20s.**

“Strong price action, retail mania, slumping vol … so bubbly,” Hartnett wrote. He then added the specific trigger that could push the market past the point of no return: the impending mega-IPOs of SpaceX and OpenAI.

“Add mega IPOs to AI big boys and market concentration easily surpasses (~48%) bubbles of roaring ‘20s, Nifty 50 ‘70s, Japan ‘80s, TMT ‘90s,” Hartnett warned.

For context: technology already accounts for over 44% of the S&P 500 Index. That’s dangerously close to the 48% threshold that marked the peak of every major historical bubble. Add a $2 trillion SpaceX and a $1 trillion OpenAI to the mix, and that threshold gets crossed with room to spare.

This is the story of how two private companies—one building rockets, the other building brains—could ignite the most concentrated, fragile, and explosive stock market in modern history. And why Hartnett believes the fuse is already burning.

## Part 2: The Professional – The Numbers Behind the Bubble

Let’s look at the hard data. Hartnett isn’t guessing. He’s counting.

### The Concentration Threshold: 48%

Here is the most important number in finance right now: **48%**. That is the approximate peak market concentration observed during every major speculative bubble in modern history.

| Historical Bubble | Peak Tech/Concentration Weight | How It Ended |

| :--- | :--- | :--- |

| **Roaring ‘20s (1929)** | ~48% | The Great Depression |

| **Nifty 50 (1973-74)** | ~48% | Oil shock, 48%+ crash in blue chips  |

| **Japan’s Bubble (1989)** | ~48% | Lost decade; Nikkei down 80% from peak |

| **Dot-Com Bubble (2000)** | ~48% | Nasdaq lost 78% |

Today, technology already accounts for more than 44% of the S&P 500. That’s just 4 percentage points away from the danger zone.

Now add SpaceX and OpenAI.

### SpaceX: The $2 Trillion Question

SpaceX is targeting the largest IPO in history with a valuation between **$1.75 trillion and $2 trillion**. For perspective, that would make it roughly the 6th-largest company in the S&P 500 on day one—right behind Broadcom and ahead of Meta.

Here’s what the prospectus reveals:

| Metric | 2025 Value | Q1 2026 Value | Implication |

| :--- | :--- | :--- | :--- |

| **Starlink Revenue** | $11.4 billion | $3.26 billion | Cash cow, 63% EBITDA margin |

| **Starlink Subscribers** | 10.3 million | — | 30% YoY growth |

| **xAI Operating Loss** | $6.36 billion | $2.5 billion | Cash furnace |

| **Total Net Loss** | $4.94 billion | $4.28 billion | Losing money at a staggering clip |

| **Price-to-Sales Ratio** | 94-107x (2025 revenue) | — | Insanely rich |

Starlink is a genuine business. It generates $11.4 billion in annual revenue with a 63% EBITDA margin and over 10 million subscribers across 164 countries. But the xAI acquisition has turned SpaceX into a money incinerator. The company burned $6.36 billion in 2025 on AI development and another $2.5 billion in the first quarter of 2026 alone. Annualized, that’s a cash burn rate exceeding $30 billion.

The valuation is equally mind-bending. At $18.7 billion in revenue, a $2 trillion target implies a price-to-sales ratio of roughly 107x. That is more than double Nvidia’s P/S multiple—a company that actually has a 75% gross margin and $58 billion in net income.

### OpenAI: The $1 Trillion Race

OpenAI is moving even faster. The ChatGPT maker is preparing to file for an IPO as early as this week or next, with a target public debut in the fall. It’s a race to market: SpaceX, OpenAI, and rival Anthropic are all scrambling to be first, because “there is only so much investor capital to go around”.

The numbers are staggering:

| Metric | Value | Source |

| :--- | :--- | :--- |

| **Latest Private Valuation** | $852 billion (March 2026) | |

| **Potential IPO Valuation** | ~$1 trillion | |

| **Microsoft’s 26.79% Stake** | Worth $228.3 billion | |

| **Microsoft’s Return on $13B Investment** | 17.6x | |

| **Projected 2026 Net Loss** | ~$14 billion | |

The company has raised $110 billion at a $730 billion pre-money valuation—the largest private funding round in history. And Microsoft is sitting on a gold mine: its 26.79% stake is worth $228.3 billion, a 17.6x return on its $13 billion investment.

But there’s a catch. OpenAI’s own projections point to a roughly **$14 billion net loss in 2026**, the cost of the infrastructure, model training, and compute needed to keep its services running.

### The Top 9 Problem

Hartnett also highlighted another uncomfortable fact: the top nine companies in the S&P 500 are all tech-related, with a combined weight of 37.7%. That’s not diversification. That’s a bet on nine horses—all from the same stable.

## Part 3: The Creative – The 48% Tipping Point

Let me give you the creative framing that explains why Hartnett is sounding the alarm.

### The “Roaring ‘20s” Parallel

The 1920s were a decade of technological revolution—radio, automobiles, electricity, assembly-line manufacturing. The stock market soared. Concentration peaked at around 48%. Then the music stopped.

The 1970s “Nifty 50” were supposed to be “one-decision stocks”—companies you could buy and hold forever. Polaroid, Coca-Cola, Eastman Kodak, Avon. They were the “Magnificent Seven” of their day. Then came the 1973-74 bear market, triggered by the Arab oil embargo and runaway inflation. The Nifty 50 collapsed. Coca-Cola fell over 60%. Polaroid plunged more than 80%. The S&P 500 tumbled 17% in 1973 and 30% in 1974.

The 1980s Japanese bubble saw the Tokyo Stock Exchange command 41% of global equities. By 1989, the Nikkei was at 38,915. By 2009, it was at 7,054.

The 1990s dot-com bubble saw the Nasdaq soar 400% in five years. Then it lost 78% of its value.

Hartnett is warning that the AI trade—magnificent as it is—may be following the exact same playbook.

### The “Retail Mania” Signal

Hartnett’s note called out three specific bubble signals that are all flashing red:

| Signal | Current Status | Why It’s Dangerous |

| :--- | :--- | :--- |

| **Strong price action** | S&P 500 up 30%+ since Iran war dip | Momentum breeds complacency |

| **Retail mania** | IPO access for SpaceX, options trading at record highs | Retail investors are “max bullish”  |

| **Slumping volatility** | VIX near 52-week lows | Markets are priced for perfection |

Bank of America’s own fund manager survey showed that investors increased their allocations to U.S. equities by the **most on record** this month, with bullish sentiment nearing extreme levels and triggering sell signals. “Consensus max bullish on Positioning & Profits,” Hartnett wrote.

When everyone is already in the pool, there’s no one left to jump in and push prices higher.

### The “Mega-IPO Curse”

Hartnett also pointed to historical data that should give pause to anyone rushing to buy SpaceX or OpenAI shares at the IPO. He reviewed some major IPOs and found that debuts like Saudi Aramco and Meta Platforms had proved “inconsequential” for the broader stock market. In some cases, markets were lower 9-12 months after “toppy” offerings like Visa and AIA Group.

The pattern is clear: mega-IPOs tend to mark the peak of a bubble, not the beginning of a new leg higher. They are the “sell” signal, not the “buy.”

## Part 4: Viral Spread – The Headlines and the Warning Signs

The news has spread rapidly across financial media, and the reaction has been intense.

### The Viral Headlines

- *“BofA’s Hartnett Warns Mega-IPOs Risk Bubble Like Roaring ‘20s”* 

- *“‘Roaring Twenties’ Return! BofA's Hartnett Warns: SpaceX Mega IPO Will Trigger an Epic Bubble”* 

- *“Tech concentration is about to surpass 48%—the level that ended every major bubble”*

- *“Hartnett says rising yields are how bubbles burst. And yields are rising.”*

### The Rising Yields Tripwire

Speaking of rising yields, here’s the other shoe waiting to drop. The 10-year Treasury yield has risen 26 basis points over the past month and is trading at a one-year high.

“A surge in bond yields is how booms and bubbles end,” Hartnett said. He identified a pair of State Street ETFs as twin indicators:

| Indicator | Trigger Level | Meaning |

| :--- | :--- | :--- |

| **Biotech ETF (speculative)** | Drops to $120 | Bond yields have continued soaring |

| **Retail Stocks ETF** | Rises to $85 | Bond-related shock has been postponed |

The biotech ETF is currently flashing yellow. If it drops to $120, Hartnett says, it would mean yields have breached a critical threshold—and the bubble-popping process would be underway.

### The Meme Angle

**Meme #1: “The 48% Line”**

An image of a measuring stick marked at 48%. The stick is labeled “Bubble Threshold.” The current market’s tech weight is 44% and rising. A tiny investor is standing on tiptoes trying to reach the 48% line. Caption: *“We’re closer than you think.”*

**Meme #2: “The Nifty 50 Ghost”**

A split image: Left side shows a 1970s photo of a Polaroid camera. Right side shows a current photo of an Nvidia GPU. Both have a ghostly “50” stamped on them. Caption: *“What goes up…”*

**Meme #3: “The Mega-IPO Curse”**

A cartoon of a giant rocket ship labeled “SpaceX IPO” and a giant brain labeled “OpenAI IPO.” Both are aimed at a bullseye labeled “Bubble Peak.” A tiny investor is standing at the bullseye, looking up. Caption: *“History doesn’t repeat, but it often rhymes.”*

### The Reddit Threads

On r/wallstreetbets and r/investing, the reactions are divided:

- *“Hartnett has been warning about a crash for two years. Even a broken clock is right twice a day.”*

- *“48% concentration is insane. The last time we saw that was 1929. Wake up.”*

- *“The difference is that AI actually has earnings. Nvidia prints money. This is not the dot-com bubble.”*

## Part 5: Pattern Recognition – What Comes Next

Let me give you the professional outlook based on Hartnett’s analysis and historical precedent.

### The Three Scenarios

| Scenario | Probability | Description |

| :--- | :--- | :--- |

| **The “Melt-Up” Scenario** | 35% | SpaceX and OpenAI IPOs go off without a hitch. Tech concentration pushes past 50%. Retail mania intensifies. The final leg of the bull market is the most explosive. |

| **The “Trading Range” Scenario** | 40% | IPOs proceed, but valuations are somewhat restrained. Tech stays near 45-48% concentration. The market grinds sideways, waiting for earnings to catch up. |

| **The “Bubble Burst” Scenario** | 25% | Yields spike. The IPOs mark the top. The Nifty 50/Japan/dot-com pattern repeats. A 20-30% correction follows. |

### The Hartnett Playbook

Hartnett’s own positioning is worth noting. He has correctly predicted the outperformance of **international equities** and has been **bullish on commodities**—both of which have paid off. He is not a doomsayer. He is a strategist who rotates out of crowded trades.

His current advice? **“No one cutting longs in stocks before historic IPOs and big top.”** But he expects “some profit taking here” because yields are breaking up.

### What This Means for You

| If you are... | Takeaway |

| :--- | :--- |

| **An AI stock investor** | The fundamentals are strong, but the positioning is extreme. Consider taking some profits before the IPOs, not after. |

| **A SpaceX or OpenAI IPO hunter** | Historical precedent suggests mega-IPOs often mark the top. Be careful. The first-day pop might be the best exit, not the entry. |

| **A diversified investor** | Check your tech concentration. If you’re over 40% in tech, rebalance. International equities and commodities are Hartnett’s preferred plays. |

| **A passive index investor** | The S&P 500 is becoming a tech fund. That’s been great. But understand the risk you’re taking. |

## Conclusion: The Tipping Point

Let me give you the bottom line.

Michael Hartnett is not predicting a crash. He is pointing at a flashing red light that has preceded every major market dislocation in the last 100 years. The 48% concentration threshold has been breached before—and every time, the outcome was painful.

**Here’s what I believe, friendly and straight:**

The AI trade is real. Nvidia’s earnings are extraordinary. SpaceX is building the future. OpenAI is redefining intelligence. But the market has already priced in a lot of that optimism—perhaps too much.

The SpaceX and OpenAI IPOs could be the “sell the news” events that mark the top of this cycle. Hartnett’s warning about rising yields is equally critical. When bond yields spike, bubbles burst. And yields are already at one-year highs.

This is not a call to sell everything and hide in cash. It’s a call to be aware. To check your concentration. To consider taking some profits. To look at international equities and commodities—the two trades Hartnett correctly called last year.

The Roaring ‘20s ended with a crash. The Nifty 50 ended with a crash. Japan’s bubble ended with a crash. The dot-com bubble ended with a crash.

The question is not whether the AI trade will eventually correct. The question is whether you’ll be positioned for the landing—or caught in the fall.

**What you should do right now:**

| Step | Action |

| :--- | :--- |

| **Step 1** | **Check your tech concentration.** If you’re heavily weighted toward AI and tech, consider diversifying into international equities and commodities. |

| **Step 2** | **Watch the 10-year yield.** A sustained move above recent highs would be the most immediate threat to tech valuations. |

| **Step 3** | **Approach the mega-IPOs with caution.** History suggests the first-day pop might be the best exit, not the entry. |

| **Step 4** | **Stay humble.** Markets can stay irrational longer than you can stay solvent. Don’t short the AI trade—just don’t bet the farm on it. |

**The final word:**

Michael Hartnett has been in the trenches long enough to recognize the smell of a bubble. The price action is strong. The retail mania is real. The volatility is low. And the mega-IPOs are coming.

The 48% threshold is not a line in the sand. It’s a line in the history books. And we are about to cross it.

The question is whether we cross it and keep climbing—or cross it and start falling.

History suggests the answer. But this time, as always, “it could be different.”

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## FREQUENTLY ASKING QUESTIONS (FAQ)

**Q1: Who is Michael Hartnett and why does his warning matter?**

**A:** Michael Hartnett is Bank of America’s chief investment strategist. He correctly predicted the outperformance of international equities last year and has been bullish on commodities—both of which paid off. When he warns about market bubbles, institutional investors pay attention.

**Q2: What is the “48%” threshold Hartnett keeps mentioning?**

**A:** The 48% threshold represents the peak market concentration observed during every major speculative bubble in modern history—the Roaring ‘20s (1929), the Nifty 50 (1973), Japan’s bubble (1989), and the dot-com bubble (2000). Technology already accounts for over 44% of the S&P 500, and mega-IPOs could push it past 48%.

**Q3: What are the mega-IPOs Hartnett is worried about?**

**A:** SpaceX is targeting a $1.75 trillion to $2 trillion IPO—the largest in history. OpenAI is preparing to file for an IPO with a potential valuation of roughly $1 trillion. Both are expected to go public in the coming months, with OpenAI targeting a fall debut and SpaceX aiming for June 12.

**Q4: How does SpaceX make money?**

**A:** Starlink is the financial engine. In 2025, the connectivity segment generated $11.39 billion in revenue, up 50% year-over-year, with an EBITDA margin of 63%. Starlink now has over 10.3 million subscribers across 164 countries. However, the xAI acquisition has turned the company into a cash furnace, with a $6.36 billion operating loss in 2025 and a $2.5 billion loss in Q1 2026 alone.

**Q5: How does OpenAI make money?**

**A:** OpenAI generates revenue through ChatGPT subscriptions, API access for developers, and enterprise AI solutions. However, the company is still deeply unprofitable, with a projected net loss of roughly $14 billion in 2026 due to the enormous cost of infrastructure, model training, and compute. Its latest private valuation reached $852 billion, and an IPO could push it toward $1 trillion.

**Q6: What does Hartnett say about rising bond yields?**

**A:** Hartnett said “a surge in bond yields is how booms and bubbles end”. The 10-year Treasury yield has risen 26 basis points over the past month and is trading at a one-year high. He uses a biotech ETF as a key indicator: if it drops to $120, it would mean yields have continued soaring and the bubble-popping process is underway.

**Q7: Is Hartnett predicting a crash?**

**A:** Hartnett is not predicting an immediate crash. He notes that “no one [is] cutting longs in stocks before historic IPOs”. But he is warning that market positioning is “max bullish,” valuations are stretched, and the combination of rising yields and mega-IPOs could trigger a significant pullback.

**Q8: What should I do with my portfolio?**

**A:** This is not investment advice. However, Hartnett suggests that diversification into international equities and commodities could be wise. He also recommends watching the 10-year Treasury yield and considering profit-taking before the mega-IPOs, rather than after.

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**Disclaimer:** This article is for informational and educational purposes only. It does not constitute financial, legal, or investment advice. Stock market investing involves risk, including the potential loss of principal. Past performance does not guarantee future results. The views expressed are those of Michael Hartnett and Bank of America as of May 2026 and are subject to change. Please consult with a qualified financial advisor before making any investment decisions.