Cash drag: T-bills vs being invested
Sitting in “safe” T-bills feels good during rough markets, but it quietly slows compounding. This study shows how much growth you leave on the table versus staying invested — and when cash actually makes sense.
Some of the links on this site are affiliate links, meaning we may earn a commission at no extra cost to you if you sign up through them. This does not affect our reviews or recommendations — we only feature products we genuinely believe are useful for investors. This site provides educational content only, not personalized investment advice. Investments can lose value and past performance does not guarantee future results. You are responsible for your own financial decisions and for confirming the tax and legal rules that apply in your country.
TL;DR
- T-bills have low drawdowns but low long-run growth.
- Staying invested in stocks means bigger swings but meaningfully more compounding.
- A “temporary” cash park that lasts years can cost more than one bad year in stocks.
Cash feels safe now, but it quietly locks in a slower compounding rate. The damage is not obvious month-to-month — it shows up after years. The longer you stay in cash, the bigger the gap.
How this study was built
Two simple paths, same timeline — no timing tricks or mid-sample switches.
100% in a broad stock index (think an S&P 500 tracker), dividends reinvested. Stays invested the entire period — no market-timing exits.
100% in a short-term Treasury / T-bill proxy (cash-like), rolling from one bill to the next. No equity exposure at any point.
Data is modeled using monthly total returns (price plus income), ignoring fund expense ratios and taxes. Both paths start at 1.00x and stay in their lane the whole time.
The chart and table use stylized paths for a 2021–2024 window to illustrate cash drag. They are not a precise recreation of any specific ETF, rate history, or backtest — the point is the shape of the gap, not the exact numbers.
What “T-bills” means here — and what this study is not
A safe, low-volatility, low-yield cash alternative — short-term Treasuries or cash-like instruments. Not a specific fund or rate series.
No shifts from cash to stocks mid-sample. Each path stays fixed to isolate the gap between staying safe and staying invested.
The chart and table use the same stylized paths; figures are rounded so the focus stays on the trade-off, not exact decimals.
This is an educational illustration. It is not personalized investment advice or a forecast of any real instrument or period.
Normalized growth: stocks vs T-bills (2021–2024)
Both paths start at 1.00x. The widening gap is the cost of playing it safe for the entire period.
Stylized chart for intuition. Real outcomes depend on the exact period and instruments used. Not a backtest of any specific fund or index.
What the data says
Stocks move up and down but (historically) have a higher expected compounding rate. T-bills barely move. The result is a meaningful gap in ending wealth — even though the T-bill path rarely “hurts.”
This is the trap: cash feels safe now, but it quietly locks in a slower compounding rate. The damage is not obvious month-to-month — it shows up after years.
| Series | CAGR | Max drawdown | Worst 12-mo |
|---|---|---|---|
| Always Invested (stocks) | approx 5.1% | approx -5.5% | approx -4.8% |
| Always in T-Bills | approx 1.9% | ~0.0% | 0.0% or better |
When cash drag is most dangerous
The longer your time horizon, the more a slow compounding rate costs you.
You tell yourself you will wait, then sit in cash for years. “Temporary” cash that never actually gets invested is one of the most common and costly mistakes.
Retirement savings and long-term goals parked in T-bills because markets feel scary. The safe feeling comes at a compounding cost that builds over 10–20+ years.
Moving to cash every time news turns negative, then waiting too long to re-enter. Each cycle resets compounding and may also trigger taxable events.
A few extra percent of return per year matters enormously over 10–20+ years. The gap between 1.9% and 5.1% CAGR does not feel large in year one. Over two decades it is transformative.
When T-bills actually make sense
The goal is not to eliminate cash — it is to put the right money in the right bucket.
Money you truly need soon — rent, taxes, a planned big purchase. If you need it within 1–2 years, keeping it in cash is not drag: it is sensible asset-liability matching.
Your emergency fund should be in cash. Liquidity is the entire point. This money is not meant to compound — it is meant to be there when you need it.
Short “in-between” windows while you move accounts or clean up your allocation. Brief parking is fine — the problem is when “brief” becomes indefinite.
If volatility reliably causes panic-selling, a small cash or T-bill allocation may actually improve long-term results by preventing worse decisions. A portfolio you can hold beats a “perfect” one you abandon.
Ready to put long-term money to work?
Move what is truly long-term money out of “forever cash” and into a real portfolio you can hold. IBKR and Trade Republic are the practical defaults for EU investors: fractional shares, recurring plans, and transparent pricing.
EU Investor Cost Toolkit — 49 EUR
One spreadsheet, 11 tabs, 739 formulas. Broker comparison, UCITS vs US ETF drag, FX drag, spread cost, cadence breakeven, and a 30-year projection with charts. Enter your numbers once — get the full picture. 30-day money-back guarantee.
Get the toolkit (49 EUR) →Go deeper
Frequently asked questions
How much cash is too much for a long-term investor?
Enough for an emergency fund and near-term expenses is sensible. Keeping many years of long-term money in cash or T-bills is typically too much — you give up most of the compounding you actually need to build wealth over time.
Are T-bills always a bad choice for investors?
No. T-bills are useful for short-term goals, emergency funds, and temporary parking. The problem is leaving long-term money there indefinitely. The issue is not the instrument — it is the duration and the money that belongs in it.
What if I am scared to invest a lump sum all at once?
Fear of bad timing is normal. A fixed DCA schedule over several months can move you into the market without sitting in cash for years waiting for a “perfect” entry. The goal is to minimize time out of the market, not find the ideal entry point.
Should I hold cash in my brokerage account or in a bank?
Emergency and day-to-day cash is often best in insured bank accounts. Investment-plan cash buckets can sit in a broker via money-market or T-bill vehicles. The bigger issue is not the container — it is leaving long-term money uninvested regardless of where it sits.
QuantRoutine provides educational content only. Nothing on this page is an offer, solicitation, or recommendation to buy or sell any security or to open an account with any specific broker. Investments can lose value, and past performance does not guarantee future results. You are responsible for your own investment, tax, and legal decisions. Always review each broker’s current terms, fees, and eligibility on their official website before opening or funding an account.
Chart and table values are stylized illustrations based on a 2021–2024 window. Not a backtest of any specific fund, ETF, or index. Real results will differ. Last updated: March 2026.