Building a fixed income allocation: from building blocks to portfolio

The first two articles in this series took a bond apart to see what drives its return, and traced how the market prices the distance between the safest and the riskiest issuers. Assembling those pieces into an allocation is a different exercise, and it is the one where investors most often start from the wrong place.

Building a fixed income allocation begins not with yield but with purpose. Once you have decided whether you want income, diversification, or capital preservation, the choices that usually feel hardest—how much duration to hold, how far down the credit spectrum to venture, whether to own bonds directly or through a fund, and whether to invest actively or passively—follow from that single decision rather than from whichever instrument happens to pay most this week.

This article covers the role of fixed income in portfolios, the tools for managing its risk, weighing active against passive strategies, and how to choose the right fixed income fund for your goals.

A fixed income allocation should start with purpose, not yield

Fixed income earns its place in a portfolio in three main ways, and those ways can pull against one another.

• Income. Bonds pay regular coupons that can fund spending or be reinvested, and an income-focused investor may accept more duration or some credit risk to raise the yield.
• Diversification. High-quality bonds have often moved differently from equities. Vanguard reports an average stock/bond correlation of around −0.32, and notes that the longer-term relationship has been predominantly negative since the early 2000s (Vanguard, The stock/bond correlation amid rising inflation).
• Capital preservation. Short-dated, high-quality bonds hold their value well and return principal on a known schedule, which suits money you may need before long.

These roles conflict more often than investors expect. Reaching for income by adding credit or duration may weaken the diversification benefit, because lower-quality bonds behave more like equities in a downturn—the very point Part 2 established. And the diversification relationship is not fixed: the stock/bond correlation turned positive during parts of 2022, so the benefit may vary through time. Past performance is not necessarily a guide to future performance or returns. The first question, then, is not what yields most, but which of these three jobs you most need fixed income to do.

Duration and laddering do most of the risk-management work

Two tools carry most of the load in managing a bond allocation’s risk: setting duration, and laddering maturities.

Duration, introduced in Part 1, is the dial for interest-rate risk. A longer-duration allocation may gain more if rates fall and lose more if they rise, so matching duration to your time horizon—shorter for near-term needs, longer for distant goals—is usually more productive than trying to forecast the path of rates.

A bond ladder spreads holdings across staggered maturities, for example bonds maturing in one, two, three, four, and five years. As each rung matures, the proceeds are reinvested at the longest rung, so the ladder provides regular liquidity, spreads reinvestment across different rate environments, and removes much of the temptation to time the market (Charles Schwab, Bond Ladders; Vanguard, Bond trading strategies).

Funds and ladders solve the same problem in different ways. A bond fund gives instant diversification across many issuers and holds a roughly constant duration, but it does not mature on a fixed date; an individual-bond ladder targets specific dates and returns principal on schedule, but takes more effort to build and diversify. Neither is universally better, and the choice follows from whether you value a fixed maturity date or broad diversification more.

How to choose a bond fund

Yield-to-maturity (YTM) and total return are the two most common metrics to evaluate suitability of bond funds, although that decision should not be based on these alone. 

YTM is the discount rate that equates a bond's price today with all its future coupon and principal payments. It is a forecast built on two assumptions: that the bond is held to maturity, and that every coupon is reinvested at the same rate. A fund does not mature on a fixed date, so the yield figure on its factsheet is typically a weighted average of the yields to maturity across its current holdings. It is a snapshot of what those holdings would earn if nothing changed, not a guarantee for the fund as a whole.

Total return is the alternative measure, and it is what a fund has actually delivered rather than what a snapshot projects. It combines the income distributed and the change in the fund's price, or net asset value, over a given period. It is usually reported as 1-year, 3-year, or since-inception figures.

Reading a fund's current yield alongside its total return history, rather than either number alone, gives a fuller picture. Yield indicates what the current portfolio might earn if conditions hold, while total return records what has already happened under a range of conditions.

Beyond yield and total return, these are information in a fact sheet that is worth paying attention to beside duration:

• Distribution yield—calculated by taking trailing distributions divided by NAV, it is worth checking how much of the coupons are paid out from the principal 
• Average duration—the portfolio's sensitivity to interest rate changes 
• Average credit quality, often shown as a ratings breakdown 
• Total return over multiple periods to evaluate how the fund performed over different market cycles
• Number of holdings and top issuer concentration—an indication of how diversified the portfolio actually is, beyond its label.
• Total expense ratio 

None of these figures is decisive alone. Duration without credit quality does not describe a portfolio's risk, and yield without total return does not describe its outcome. These metrics should be evaluated against the role each bond fund is meant to play in a portfolio—income, diversification, or capital preservation.

The active-versus-passive choice is about strategy, not product labels

It helps to separate two ideas that are routinely confused. An index fund is a product, built to track a chosen benchmark. Passive investing is a strategy, one that seeks to match market returns rather than beat them. The two are related, but an index fund is one way to implement a passive approach, not a synonym for it—and the distinction matters more in bonds than most investors realise.

The choice itself is a strategy decision. As FINRA frames it, passive investors generally seek to match market returns, while active managers aim to exceed market performance, with no guarantee of doing so (FINRA, Active vs. Passive Investing).

Start with the benchmark itself, because bond indices are built differently from the equity indices most investors already understand. A typical equity index weights companies by free-float market capitalisation: share price multiplied by the shares available to trade. The more valuable the market judges a company to be, the larger its slice of the index.

Bond indices use a different logic. Most, including the Bloomberg US Aggregate Bond Index—the most widely tracked benchmark for US investment-grade bonds—weight each issuer by the market value of its debt outstanding. An issuer's slice of the index grows the more it has borrowed, which may introduce more risk than expected.

Additionally, issuer outcomes vary widely and credit ratings may not be static. Bond index funds operate under mandates that permit them to hold only bonds of a minimum credit rating—downgrades can force selling at poor prices, impacting total returns. Meanwhile, this could offer opportunities for active managers that are not bound by the same mandate.

One lever, meanwhile, works in either approach: cost compounds, so keeping it low is among the few advantages an investor controls directly.

Building the allocation in the right order

The sequence matters more than any single instrument. Decide the role first—income, diversification, or preservation—then set duration and credit quality to match, then choose between direct bonds and funds, and only then compare yields.

Most investors are better served by starting from purpose than from the highest headline rate. On the one hand, direct government bonds such as Singapore Savings Bonds offer simplicity and capital security up to a stated limit; on the other, bond funds offer diversification and professional management across a far wider opportunity set, including the corporate and global bonds an individual would struggle to assemble alone. Neither approach dominates, and the better choice depends on the job the allocation is meant to do.

Endowus provides access to institutionally managed bond funds and cash management solutions on a low, fee-only basis, so more of the yield stays with the investor. Start investing with us today.

Read more in our fixed income series:

• Part 1: Bond yields and duration: what every investor needs to know
• Part 2: Investment Grade vs High Yield: understanding the credit spectrum

Frequently asked questions

What role do bonds play in a portfolio?

Bonds mainly provide income, diversification against equities, and capital preservation. Which role dominates depends on the bonds you choose—high-quality government bonds lean toward diversification and preservation, while credit and longer duration lean toward income and return.

What is a bond ladder?

A bond ladder holds bonds that mature in staggered years. As each matures, the proceeds are reinvested at the longest maturity. It provides regular liquidity, spreads reinvestment across rate environments, and reduces the need to time the market.

What is the difference between an index fund and passive investing?

An index fund is a product that tracks a benchmark. Passive investing is a strategy that seeks to match market returns rather than beat them. An index fund is one way to invest passively, but the two terms are not interchangeable.

What government bonds can I buy directly in Singapore?

In Singapore, individuals can buy Singapore Savings Bonds, SGS bonds, and Treasury bills. Terms and availability vary by issuance.

Are bond funds better than individual bonds?

Neither is universally better. Funds offer instant diversification and professional management but no fixed maturity date; individual bonds return principal on a known date but take more effort to diversify. The right choice depends on your objective.