Studies going back to the 1980s (Brinson, Hood, Beebower; repeated many times) consistently show: asset allocation explains about 90% of portfolio return variance over long periods. Stock picking, timing, everything else — that’s 10%.
In other words: whether your portfolio is 80% stocks / 20% bonds vs 50% stocks / 50% bonds matters dramatically more than which specific stocks or funds you pick.
Today’s lesson is about asset allocation. The single most important investment decision, and the one most beginners skip past to obsess over which ETF to buy.
The basic division
Most portfolios divide across a few broad asset classes:
- Stocks (equities): higher expected return, higher volatility. 5-7% real long-term.
- Bonds (fixed income): lower expected return, lower volatility. 1-3% real.
- Cash: near-zero real return, very low volatility.
- Alternative assets (real estate, commodities, gold): varied characteristics.
Most retail portfolios are adequately covered by stocks + bonds + some cash. Alternatives add complexity and rarely justify themselves for beginner-to-intermediate investors.
How to pick your stock/bond ratio
Three main considerations:
1. Time horizon
The most important factor. When will you need the money?
- Less than 3 years: cash or short-term bonds. Not stocks.
- 3-10 years: mostly bonds, some stocks (30-50%).
- 10-20 years: balanced (50-70% stocks).
- 20+ years: mostly stocks (70-100%).
The reason: stocks’ volatility is scary over 1-5 year windows but tends to produce positive real returns over 15-20+ year windows. Bonds are the opposite — reliable short term, eroded by inflation long term.
2. Risk tolerance
Not theoretical. Actual. How did you feel during the last bear market?
- If you panic-sold in 2022: you’re less risk-tolerant than you thought. Dial back stocks.
- If you kept investing through 2008-2009: you can handle volatility. More stocks fine.
- If you’re new and untested: be conservative at first. You can shift more to stocks as you prove emotional resilience.
Portfolio you can stick with > theoretically optimal portfolio you abandon in a crash.
3. Need for stability
Some income sources are stable (Italian public-sector pension, tenured employment). With a stable base, you can take more portfolio risk.
Others are volatile (freelancing, commission-based, startup equity). With volatile income, your portfolio should be steadier to avoid double-trouble in downturns.
Age-based glide paths
A common heuristic: % in stocks = 110 − your age.
Examples:
- Age 25: 85% stocks, 15% bonds.
- Age 40: 70% stocks, 30% bonds.
- Age 60: 50% stocks, 50% bonds.
- Age 75: 35% stocks, 65% bonds.
More aggressive variant: 120 − age (popular among FIRE community). Gives:
- Age 25: 95% stocks.
- Age 60: 60% stocks.
Neither formula is “right.” They’re starting points. Adjust based on your specific time horizon, other income sources, psychological tolerance.
The Boglehead three-fund portfolio
A widely-recommended simple structure:
- Domestic equity ETF (or regional: European or Italian).
- International equity ETF (the rest of the world).
- Domestic bond ETF.
For an EU-resident Italian investor, adapted:
- Global equity ETF (FTSE All-World or MSCI ACWI): 60-80%.
- European aggregate bond ETF: 15-35%.
- Optional: tilt toward factor (small-cap, value) or Italian exposure for home preference.
Simple, low-cost, adequately diversified, easy to rebalance.
Sofia’s portfolio plan (age 28)
She’s 28, stable employment, 35-year horizon to retirement, no dependents yet, moderate-to-high risk tolerance.
Her target allocation:
- Global equity ETF: 75% (e.g., Vanguard FTSE All-World, TER 0.22%).
- EU aggregate bonds: 20% (e.g., iShares Core € Govt Bond, TER 0.09%).
- Cash buffer: 5% (conto deposito).
Expected real return: ~5% per year. Expected volatility: ~14%.
At 75% stocks and 28 years old, she’s fairly aggressive — appropriate for her horizon.
Giorgio’s portfolio plan (age 52)
Stable teacher income, 15 years to pension, lower risk tolerance (doesn’t want to see significant losses near retirement).
His target allocation:
- Global equity ETF: 50%.
- Mix of BTP and EU bond ETF: 40%.
- Cash: 10%.
Expected real return: ~3.5% per year. Expected volatility: ~9%.
More conservative than Sofia, because he has less time to recover from a crash and is closer to needing the money.
Luca’s portfolio plan (age 18, limited savings)
Small amounts, 45+ year horizon, no major commitments yet.
His target allocation:
- 100% global equity ETF.
At 18 with €200/month PAC, there’s no point in holding bonds — over 45 years, equities will dominate bonds. The volatility is fine because he won’t need the money for decades.
As he approaches age 30 and his wealth grows, he can start adding bonds.
The “home bias” decision
Italian investors often overweight Italian stocks or European stocks. The math:
- Italy is ~0.7% of global market cap.
- Eurozone is ~9% of global market cap.
- US is ~63%.
A global market-cap-weighted portfolio holds ~63% in US stocks. Many European investors feel uncomfortable with that. Reasonable compromise:
- Global index: 60% (which includes US weight naturally).
- Europe tilt: 15-30% in STOXX Europe or Euro STOXX ETF.
- Optional Italy tilt: 5-10% in FTSE MIB ETF.
If you want Italian/EU overweight, do it consciously and limit it. 30-50% home bias is too much for long-term returns.
Real estate as part of the allocation
For Italians, real estate is often the largest single asset. If you own your primary residence, it’s typically 40-70% of your net worth.
Should this count as “alternative assets” in the allocation?
Practical advice: treat primary residence as consumption, not investment. You live there; it’s not primarily a wealth-building tool. Your “investable assets” are separate — stocks, bonds, retirement accounts.
If you also own investment property (second home rented out), count that separately as a real estate allocation. It’s illiquid and concentrated but does provide diversification from financial markets.
Adding complexity (when to, when not to)
As you get more experienced, you might consider:
Factor tilts
Small-cap value tilt, momentum ETFs, quality ETFs. Historically add 0.5-1.5% long-term. Require discipline during underperformance periods.
Reasonable for intermediate investors. Skip for first 5 years of investing.
Commodities
Gold, broad commodities ETFs. Can hedge against inflation. Correlation with stocks is low.
Small allocation (5-10%) reasonable if you want inflation protection beyond bonds. Not strictly necessary.
Inflation-linked bonds
BTP Italia, BTP indicizzati eurozone HICP. Specifically protect against inflation.
Reasonable slice (10-20% of bond allocation) for retired or near-retired investors. Younger investors generally fine without.
Emerging markets
Separate ETF tilt toward EM. MSCI ACWI already includes ~10% EM; if you want more, add EM-specific ETF.
Reasonable. Adds diversification and long-term expected return. Also adds volatility.
REITs (real estate ETFs)
Public real estate exposure. REITs are legally required to distribute most income; they behave somewhat between stocks and bonds.
Optional. For Italian investors, primary residence already provides real estate exposure, so REITs are less critical.
What to avoid
- Concentrated single-stock bets beyond 5-10% of portfolio.
- Active mutual funds (lesson 25).
- Structured products at banks.
- Crypto as a major allocation (speculative; 0-5% max if at all, treated as entertainment).
- “Hot tips” and themed ETFs (EV-only, AI-only, cannabis-only). Narrow themes.
Revisiting the allocation
Life events change what’s right:
- Marriage or cohabitation: joint horizon, coordinate allocations.
- Children: longer horizon on some savings; shorter on others.
- Buying a house: cash buffer for down payment shifts to shorter-term assets.
- Career change: may affect stable income assumption.
- Retirement approaching: shift toward bonds and cash.
- Inheritance: rebalance to avoid concentration in inherited assets.
Review your asset allocation annually. Make major changes only when life changes — not in response to market news.
What to do with this lesson
Three things:
- Write down your target allocation. Specific percentages: stocks, bonds, cash. Tape to your wall.
- Compare to your current portfolio. If they’re far apart, make a plan to shift over 6-12 months (not all at once, to avoid market-timing risk).
- Don’t change allocation based on market news. Change only when your circumstances change.
Sources
- Brinson, Hood, Beebower — Determinants of Portfolio Performance, Financial Analysts Journal, 1986 (original asset allocation study).
- William Bernstein — The Four Pillars of Investing, 2002.
- John Bogle — Common Sense on Mutual Funds, 1999.
- Vanguard — Principles for Investing Success.
https://corporate.vanguard.com/content/corporatesite/us/en/corp/how-we-invest/principles-for-investing-success.html.
Next lesson: diversification — what it is and what it isn’t. Systematic vs idiosyncratic risk. Why five Italian stocks aren’t diversified.