From January 2015 to July 2026, a plain 60/40 portfolio of US shares and US bonds compounded at 8.97% a year. Add a 1% bitcoin sleeve, rebalanced monthly so it stays at 1%, and that becomes 9.61%. Push the sleeve to 5% and it becomes 12.17%.
Those are the headline numbers. They're also the least interesting thing on this page. What matters far more is how quickly they fall apart when you shift the start date by a few years.
Start the same test in January 2025 instead and the 5% sleeve doesn't add 3.2 points a year. It subtracts 1.7. Same asset, same rebalancing rule, same end date. Only the window moved.
How these figures are built
Everything below is computed from month-end total-return series: the SPDR S&P 500 ETF for shares, the iShares Core US Aggregate Bond ETF for bonds, and the BTC-USD reference price, all pulled from Yahoo Finance. The window runs from 31 December 2014 to 31 July 2026, which is 139 monthly returns.
The bitcoin sleeve is funded pro-rata from both sides, so a 5% sleeve sits beside 57% shares and 38% bonds. Sharpe ratios use the three-month Treasury bill rate from the St Louis Fed. Unless stated otherwise, the portfolio is rebalanced back to target every month, which is the strictest possible reading of "a 1% allocation".
What a small sleeve did over the full window
| Bitcoin sleeve | Return a year | Volatility | Max drawdown | Sharpe |
|---|---|---|---|---|
| None (60/40) | 8.97% | 9.85% | -20.05% | 0.72 |
| 1% | 9.61% | 10.01% | -20.46% | 0.77 |
| 2% | 10.26% | 10.23% | -20.87% | 0.81 |
| 3% | 10.89% | 10.48% | -21.28% | 0.85 |
| 5% | 12.17% | 11.09% | -22.10% | 0.91 |
Read across the rows and the trade looks lopsided in bitcoin's favour. A 5% sleeve added 3.2 percentage points of annual return, cost 1.2 points of annualised volatility, and cost roughly 2 points of maximum drawdown. The Sharpe ratio moved from 0.72 to 0.91.
The drawdown column is the one that surprises people. Bitcoin fell 75.6% on month-end prices between December 2017 and January 2019, and another 73.0% between October 2021 and December 2022. Neither collapse did much to a rebalanced sleeve. The worst 60/40 drawdown in this window bottomed in September 2022 at -20.05%, and with 5% bitcoin alongside it reached -22.10%.
That isn't luck, it's arithmetic. A 5% position that halves costs the portfolio 2.5%. Equities falling 25% cost it 15%. At these weights bitcoin can't compete with shares for control of the drawdown, which is a useful reminder that drawdown and standard deviation measure different kinds of risk and don't have to move together.
Matt Hougan and David Lawant reached the same conclusion in a 2021 CFA Institute Research Foundation brief. Their wording: average maximum drawdown "remains largely flat for allocations to bitcoin between 0% and 4% because at this size allocation, bitcoin never competes with the equity allocation to drive the portfolio's maximum drawdown". Above 4%, they found each extra percentage point of bitcoin added about one point of drawdown.
The window does nearly all the work
Here's the same 5% sleeve, same monthly rebalancing, same July 2026 end date, run from different starting points.
| Start | 60/40 a year | With 5% bitcoin | Difference |
|---|---|---|---|
| Jan 2015 | 8.97% | 12.17% | +3.19pp |
| Jan 2018 | 9.42% | 10.88% | +1.46pp |
| Jan 2021 | 8.61% | 9.66% | +1.05pp |
| Jan 2024 | 13.37% | 14.06% | +0.69pp |
| Jan 2025 | 12.36% | 10.68% | -1.68pp |
The benefit shrinks by a factor of more than four between a 2015 start and a 2024 start, then turns negative. Nothing about the asset changed. The later windows just contain less of bitcoin's early repricing and more of its recent one.
One calendar year carries an outsized share of the whole result. Bitcoin returned 1,369% in 2017. Strip 2017's twelve monthly returns out of the series entirely and the full-window gap from a 5% sleeve falls from 6.88 points a year to 2.53 under annual rebalancing. A single year, on either side of which you'd have had no way to know it was coming.
The recent record is bleaker than most allocation notes admit. Bitcoin lost 6.3% in 2025 and a further 28.2% in the first seven months of 2026. At the end of July 2026 it sat at $62,814, which is 45.7% below its month-end peak of $115,758 in July 2025. Across calendar 2025 a monthly rebalanced 5% sleeve turned a 13.56% year for the 60/40 into 12.79%.
Rebalancing changes the answer almost as much
Two portfolios can both be described as "1% bitcoin" and produce wildly different outcomes. The difference is what happens after the first month.
Rebalanced monthly from January 2015, a 1% sleeve added 0.64 percentage points a year. Rebalanced once a year at each December, the same 1% sleeve added 1.54 points, because it was allowed to run inside the calendar year and 2017 was a calendar year. Never rebalanced at all, the 1% sleeve added 4.68 points a year over an unrebalanced 60/40 baseline.
That last figure comes with a catch. A 1% sleeve bought at the end of 2014 and left alone would have been 38.8% of the portfolio by July 2026. A 5% sleeve would have been 76.8%. Whatever that portfolio is, it isn't a 60/40 with a small satellite. The 5% version ran at 41.2% annualised volatility with a worst drawdown of -63.3%. That's a bitcoin fund wearing a 60/40 costume, and it shows why a 60/40's weights drift materially inside a single year even without a bitcoin sleeve in the mix. That headline figure is contested: Fulkerson, Jordan, Riley and Yan, writing in the Financial Analysts Journal in 2026, rebuilt the calculation on the same sample and put the cost of poor timing at 0.10% a year rather than 1.2%.
Anyone reporting bitcoin-sleeve results without naming the rebalancing rule has left out roughly half the answer. The choice between annual rebalancing and 5% threshold bands is normally a second-order decision. With an asset this volatile, it's first-order.
What the published research says
The BlackRock Investment Institute published its position in December 2024, in a note by Paul Henderson, Vivek Paul, Samara Cohen and Robert Mitchnick. Their conclusion: "a 1-2% allocation to bitcoin is a reasonable range for a multi-asset portfolio if investors believe it will become more widely adopted and can bear the risk of potentially rapid price plunges".
The reasoning is risk budgeting rather than return forecasting. A 1-2% weight, they wrote, "contributes to overall portfolio risk at levels comparable to a single 'Magnificent 7' stock in a 60/40 portfolio". Beyond 2%, they argue that portfolio risk rises disproportionately.
My own numbers land close to that. On monthly returns over this window, a 1% sleeve accounts for 2.9% of portfolio variance, a 2% sleeve for 6.4%, and a 5% sleeve for 19.6%. The sleeve's share of risk grows about four times faster than its share of capital.
Academic work points somewhere very different. Yukun Liu and Aleh Tsyvinski, in a 2018 NBER working paper later published in the Review of Financial Studies, ran a Black-Litterman exercise on bitcoin data from January 2011 to May 2018. An investor who believed bitcoin would keep performing as it had should have held 6.1%. Even at half its historical performance, the model said 3.1%. Their wider finding is the one that matters more: cryptocurrencies "have no exposure to most common stock market and macroeconomic factors", and their measured correlation with stocks over that sample was 0.16.
The 2021 CFA Institute brief found that a quarterly rebalanced 2.5% sleeve, from January 2014 to September 2020, lifted a 60/40's cumulative return by 23.9 percentage points while volatility barely moved, at 10.5% against 10.3%. Sharpe went from 0.54 to 0.75. Worth knowing who wrote it: Hougan is chief investment officer of Bitwise Asset Management and Lawant was a researcher there. The brief is careful and its caveats are honest, but a bitcoin asset manager produced it.
The case against reading any of this forward
This is the strongest objection, and it doesn't come from sceptics. It comes from BlackRock.
The same note that lands on 1-2% says the greatest return potential "lies in the period before widespread adoption, when expectations and narratives may drive repricing". It then adds that widespread adoption "would dull bitcoin's key driver for further sizable price rises" and would make the case for a permanent holding less clear.
Read those two sentences together and the backtest above stops being evidence of a risk premium. Bitcoin went from $320 at the end of 2014 to $62,814 in July 2026, a 196-fold move at a 57.7% annual rate. That is what a one-time repricing looks like when an asset moves from fringe to exchange-traded product. A repricing pays once. Bond coupons and equity earnings pay repeatedly, which is why their historical records carry information about the future in a way this one may not.
Vanguard's stated reason for declining to launch its own crypto funds points at the same gap. The firm says it focuses on "products that generate cash flow in a transparent way, such as interest payments and dividends". Bitcoin has no coupon, no earnings and no dividend, so every pound of its return has to come from what the next buyer pays.
The Hougan and Lawant brief concedes the point in its own way: the 2014-2020 result "is notable, but it is also unsurprising: it captures a period during which bitcoin's price appreciated substantially". They also record that bitcoin has had six bear markets of more than 70%, and that with volatility that large "the choice of the starting point can have a dramatic impact".
There's a second problem with the sample. It's short. There are 139 monthly observations of an asset running at about 72% annualised volatility, which puts the standard error on its average annual return at roughly 21 percentage points. The arithmetic average return itself is 69.9% a year. That uncertainty swamps whatever weight an optimiser hands back. The gold literature has the same argument attached to it, which is why the 5-10% gold case struggles with its own 45-year record despite a far longer sample.
The diversification argument has been weakening
Bitcoin's case in a portfolio rests partly on low correlation with shares. That correlation has been drifting up.
On monthly returns against the S&P 500 ETF, bitcoin's correlation was 0.27 from 2015 through 2020. From 2021 through July 2026 it was 0.48. Over the whole window it's 0.35, well above the 0.16 that Liu and Tsyvinski measured on 2011-2018 data.
BlackRock flagged exactly this risk, describing bitcoin's correlations as unstable and warning that investors "may not be able to rely on it as reliable cushion against risk-off sentiment hitting other parts of the portfolio". A rising correlation and a maturing investor base are the same phenomenon seen from two angles. As bitcoin became something institutions hold in a risk budget, it started behaving like the other things in that risk budget.
The Bank for International Settlements looked at who was actually doing the holding. In a February 2023 bulletin, Giulio Cornelli, Sebastian Doerr, Jon Frost and Leonardo Gambacorta found that almost three-quarters of users downloaded a crypto exchange app when bitcoin was above $20,000, and concluded that retail investors "have chased prices, and most have lost money". Realised investor returns and asset returns are not the same number, and reported crypto fund flow data measures something narrower than it appears to.
UK participation is falling as prices fall. The Financial Conduct Authority's 2025 consumer research found that the share of UK adults holding cryptoassets dropped from 12% in 2024 to 8% in 2025, on a nationally representative sample of 2,353 people. Bitcoin was still the most commonly held, at 57% of users.
What would change the conclusion
Three things would move this materially, and all three are observable.
The first is another repricing on the scale of 2017 or 2020. If bitcoin triples again, every number in the table above shifts up and the start-date sensitivity gets worse, not better. That's not a forecast, it's a description of how the arithmetic behaves.
The second is correlation. If the monthly correlation with equities settles above roughly 0.6 for a multi-year stretch, the diversification argument stops working and the sleeve becomes leveraged equity beta with worse tails. The move from 0.27 to 0.48 is already halfway there.
The third is volatility. Bitcoin ran at about 72% annualised over this window. If widespread adoption compresses that towards 30%, a 1-5% sleeve becomes almost invisible in a portfolio, and the risk-budgeting case for capping it at 2% loses its force. That would be a different asset requiring a different analysis.
What wouldn't change the conclusion is another year of backtests. The window is the finding here. Anyone quoting a single number for what bitcoin did to a 60/40 is quoting a start date they chose, and critics of these studies are right to press on that point before anything else.