Bitcoin vs Index Funds: Where Should Your First $20 Go?

Every financial advisor in the country gives the same advice to beginners: buy an index fund. Set it and forget it. You will earn about 10% a year. In 30 years, you will be fine.

That advice is not wrong. It is just incomplete.

Roughly 90% of actively managed funds fail to beat a simple S&P 500 index fund over 15 years, according to the S&P Global SPIVA Scorecard (2025). Index funds are one of the most reliable wealth-building tools ever created. If you buy one and hold it for decades, you will almost certainly make money.

But "almost certainly make money" and "keep up with the rate at which your purchasing power is being eroded" are two different promises. And only one of them gets made.

We took Untaught's dataset of 158 months of Bitcoin prices and ran a simple test: what happens if you put $20 a week into Bitcoin versus an S&P 500 index fund? Same money. Same discipline. Same timeline. The results tell a story nobody in either camp wants to admit is complicated.

Related reading: Bitcoin vs the Stock Market | DCA vs Lump Sum | What Is Dollar Cost Averaging? | Bitcoin for Beginners

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What Is an Index Fund?

An index fund is a basket of stocks that mirrors a market index. The most popular one tracks the S&P 500, which holds shares in 500 of the largest companies in America: Apple, Microsoft, Amazon, JPMorgan, Johnson & Johnson, and 495 others.

Instead of picking individual stocks and hoping you chose right, you buy the whole market. When the market goes up, your fund goes up. When it drops, you drop with it. No decisions required.

Index funds charge almost nothing. Vanguard's S&P 500 ETF (VOO) charges 0.03% per year, which means $3 per $10,000 invested. Fidelity offers index funds at 0.00%, literally free (Vanguard, 2025; Fidelity, 2025). No financial advisor. No management fees. No "2 and 20."

The S&P 500 has returned roughly 10.5% annualized since 1957. That includes every crash, recession, and panic in modern history. Over the recent 5-year stretch (2021-2025), it returned 14.4% annualized, buoyed by a historic tech rally.

You can start with $1 through fractional shares on most major brokerages. It is as close to a "default" investment as exists.

So why would anyone look elsewhere?

We Put $20/Week Into Both. Here Are the Real Numbers.

We ran three scenarios using real price data. Bitcoin prices come from Untaught's 158-month dataset (January 2013 through February 2026, monthly closing prices). S&P 500 returns use actual annual total returns with dividends reinvested.

The investment: $86.67 per month ($20/week equivalent). Same amount, same start date, same discipline. The only difference is where the money went.

Period	Total Invested	Bitcoin Value	BTC Return	S&P 500 Value	S&P Return
3 years (Mar 2023 - Feb 2026)	$3,120	$3,779	+21%	$4,155	+33%
5 years (Mar 2021 - Feb 2026)	$5,200	$8,311	+60%	$7,729	+49%
10 years (Mar 2016 - Feb 2026)	$10,400	$164,348	+1,480%	$22,973	+121%

Bitcoin values calculated from Untaught's btc-monthly-prices.json dataset. S&P 500 values use actual annual total returns (SlickCharts, 2016-2025) compounded monthly.

Read those numbers again. Over 10 years, $20 a week turned into $164,348 in Bitcoin versus $22,973 in an S&P 500 index fund. Same money, same effort, 7x the result.

But there's a reason most people didn't actually hold through that entire 10-year window.

Why the Index Fund Won Over 3 Years

Look at the 3-year row. The S&P 500 won, $4,155 to $3,779. How?

Timing. Bitcoin's price at the end of the window, February 2026, was about $66,100. That is roughly 48% below its all-time high of $126,000 hit in October 2025. The 3-year DCA investor was buying through a recovery, a rally, and then a crash. The final months dragged the total value down.

The S&P 500, by contrast, had three consecutive strong years: +26.3% in 2023, +25.0% in 2024, and +17.9% in 2025. No major drawdown in that window. Steady upward march.

This is not an edge case. It is the core reality of the comparison. Bitcoin's returns are not evenly distributed. They come in bursts. Between those bursts are periods where the index fund quietly pulls ahead.

The S&P 500's worst calendar year in this window was 2022 at -18.1%. Bitcoin's worst was -64.3% that same year. When both drop, Bitcoin drops harder. When both recover, Bitcoin recovers harder. Whether that is good or bad for you depends entirely on when you check the scoreboard.

Why Bitcoin Won Over 10 Years

The 10-year numbers are hard to argue with. BTC turned $10,400 into $164,348. The S&P 500 turned the same amount into $22,973. That is a $141,000 difference on $200 a month.

How? The math of asymmetric returns.

The S&P 500 compounds steadily. A good year is +25%. A great year is +30%. It rarely doubles. Over 10 years, those returns stack predictably into 2-3x your money.

Bitcoin does something different. It has calendar years where it returns +124% (2016), +1,338% (2017), +303% (2020), +155% (2023), and +121% (2024). A single year can return what the S&P 500 takes a decade to deliver.

Bitcoin's mean monthly return from 2016 to 2024 was 7.8%, compared to 1.1% for the S&P 500, according to Fidelity Digital Assets (2024). Over short windows, that gap can flip or disappear. Over long windows, it compounds into a different universe.

Here is the uncomfortable part: the DCA investor who held Bitcoin through the 10-year period endured a 73% crash (2018), a 64% crash (2022), and a 48% drawdown (2025-2026). Holding through those required watching years of gains evaporate and doing nothing. The index fund investor never experienced anything worse than -18%.

The Risk That Changes Everything

This is where the conversation gets honest.

Bitcoin's annualized volatility runs roughly three to four times higher than the S&P 500's. Fidelity Digital Assets found that Bitcoin was consistently "three to nearly four times as volatile as equity indices" over the 2020-2024 period (Fidelity Digital Assets, 2024).

The numbers look clean in a table. They do not feel clean when you live through them.

Metric	Bitcoin	S&P 500 Index
Annualized volatility	~54%	~13%
Max drawdown (lifetime)	-93% (2011)	-57% (2008-09)
Drawdowns exceeding 50%	4 since 2014	2 since 1957
Recovery from worst crash	~3 years	~5.5 years
Sharpe ratio (2020-2024)	0.96	0.65

Volatility data from Fidelity Digital Assets (2024) and BlackRock iShares (Jan 2025). Recovery data from NYDIG Research (2025).

The Sharpe ratio, which measures return per unit of risk, actually favors Bitcoin (0.96 vs 0.65). On a purely mathematical basis, Bitcoin delivered better risk-adjusted returns over the 2020-2024 window. But the Sharpe ratio does not measure how it feels to watch your portfolio drop 76% in a single year.

Research from Coinbase and Ipsos (Q4 2025) found that 73% of younger adults say it is harder for their generation to build wealth through traditional means. That frustration is part of why 45% of Gen Z and millennial investors own crypto, compared to 18% of older generations.

The question is whether that frustration leads you to an asset you can actually hold through its worst moments. If a 50% crash makes you sell, Bitcoin's superior long-term returns do not matter. You will never see them.

Where Index Funds Win

Index funds have real advantages that Bitcoin cannot replicate.

Decades of track record. The S&P 500 has data going back to 1957. Every recession, every war, every crisis is in the dataset. Bitcoin has 13 years of meaningful trading history. The index fund's floor is better understood because we have seen more of it.

Tax-advantaged accounts. You can hold index funds in a 401(k), Roth IRA, or HSA. Employer matches double your money before the market does anything. A 100% return on day one, guaranteed, with zero risk. Bitcoin does not qualify for employer matching (yet), and holding it in tax-advantaged accounts is complicated.

Dividends. The S&P 500 pays dividends, roughly 1.3% annually. Those dividends get reinvested automatically and compound over time. Bitcoin generates no income. It appreciates or it doesn't.

Lower volatility. The S&P 500's worst calendar year in the last two decades was -38.5% in 2008. Bad, but you recovered in about 5.5 years. Bitcoin has dropped more than 75% four times in its history. The emotional cost of holding through those drawdowns is higher, and most people pay it by selling at the bottom.

Easier to explain. "I own a piece of the 500 biggest companies in America" is a sentence everyone understands. "I own a decentralized, scarce digital bearer asset secured by proof-of-work consensus" is a sentence that makes people's eyes glaze over. If you cannot explain your investment to yourself, you are more likely to panic when it drops.

Where Bitcoin Wins

Bitcoin has advantages that index funds cannot replicate either.

No gatekeepers. You do not need a brokerage account, a Social Security number, or a credit check to buy Bitcoin. You need a phone and $1. Strike and Cash App both let you buy with no minimums. Only 62% of Americans own stock (Gallup, 2025). The other 38% are locked out by inertia, complexity, or financial barriers. Bitcoin removes those barriers.

24/7 markets. The stock market is open Monday through Friday, 9:30 AM to 4:00 PM Eastern. Bitcoin trades 24 hours a day, 365 days a year. You can buy, sell, or check your portfolio at any time. No waiting for the opening bell.

Asymmetric upside. The S&P 500 will probably not 10x in the next decade. It never has. Bitcoin has 10x'd multiple times. If your goal is to turn a small amount of money into a meaningfully larger amount, Bitcoin offers a path that index funds mathematically cannot. That comes with more risk, but for someone starting with $20 a week, the downside is $20, and the upside is uncapped.

A hedge against monetary expansion. Index funds are priced in dollars. If the dollar loses purchasing power, your nominal gains may not translate to real gains. Bitcoin's fixed supply of 21 million coins means it cannot be diluted. When governments print more money, your index fund goes up in dollar terms but may go sideways in purchasing power terms. Bitcoin's thesis is that it does not have this problem.

Self-custody. You can hold your own Bitcoin. Nobody can freeze it, seize it, or prevent you from accessing it. Your index fund lives inside a brokerage that can restrict withdrawals, go bankrupt, or comply with a government order. That difference may not matter to most people today. It might matter more tomorrow.

The Honest Answer

You do not have to choose one.

Both Bitcoin and S&P 500 index funds now let you start with $1. Both support automated recurring purchases. Both reward consistency over decades. The $20/week you redirect from lottery tickets, forgotten subscriptions, or impulse buys can go into either, or split between both.

There is no rule that says your first $20 must go to one place forever.

Here is a framework that fits the Untaught thesis:

If you want the safest starting point: An S&P 500 index fund. Open a Roth IRA, set up automatic $20/week contributions. You will sleep well at night, earn roughly 10% annually over the long run, and never have to watch your portfolio drop 75%.

If you want to fight back against the system: Bitcoin. Open Strike, set up automatic $20/week purchases. You are opting out of a monetary system designed to erode your purchasing power. The ride will be rougher, but the destination might be worth it.

If you want both: Split it. $10/week into an index fund, $10/week into Bitcoin. You get the stability of the stock market and the asymmetric upside of Bitcoin. As you learn more and understand your own risk tolerance, you can adjust the split.

Gen Z started investing at age 19 on average, compared to 35 for Boomers (Schwab Modern Wealth Survey, 2024). That head start matters more than which asset you pick first. Getting years of compounding, in anything, beats debating the perfect allocation while your money sits losing value.

The Bottom Line

Index funds are the safest, most reliable wealth-building tool for most people. That has not changed. The data supports it, and 70 years of history backs it up.

Bitcoin is the highest-returning asset of the last decade, with a risk profile that most people underestimate. The data supports that too.

Over 3 years, the index fund won. Over 5 years, they were nearly tied. Over 10 years, Bitcoin turned $10,400 into $164,348 while the index fund turned it into $22,973.

Neither of those facts makes the other one wrong. They just describe different trade-offs, different tolerances for chaos, and different beliefs about where the world is headed.

You have $20 this week. The market is open. Start investing.

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This article is part of the Small Steps, Real Results series on Untaught. The first step isn't finding the perfect investment. It's just starting.