Yield to Maturity and the Coupon Reinvestment Assumption

Summary

The document raises practical questions about the reinvestment assumption behind yield to maturity (YTM): coupon payments may be too small to buy another bond, and newly issued Treasury maturities may not match the investor’s remaining holding period. It also questions whether investors who need bond income actually reinvest their coupons. The discussion frames YTM as a return measure that depends on what happens to coupon cash flows, rather than a guaranteed realized return.

The document provides questions, not a full explanation or empirical comparison of yield measures. It does not establish that actual returns must be lower, nor does it recommend an alternative metric. Its examples concern fixed-rate government bonds, and the practical outcome depends on the bond, purchase terms, reinvestment choices, and investor’s holding period. Readers should treat it as a prompt to distinguish a quoted yield from realized holding-period returns, not as a complete guide to calculating either.

Key ideas

• YTM reflects assumptions about coupon cash flows over the investor’s holding period.
• Coupon size and available bond maturities can constrain practical reinvestment choices.
• An investor who spends coupon income will not realize the same outcome as one who reinvests it.
• The document poses questions about alternative yield measures but does not answer them.

Tags

# Realistic understanding of YTM and reinvestment


# Realistic understanding of YTM and reinvestment












Studying for CFA level 1 right now and there are a couple questions I have about YTM and reinvestment rates. It states the following: There are three sources of returns from investing in a fixed-rate bond: "...Interest earned on coupon payments that are reinvested over the investor's holding period for the bond..."

There are a couple issues in understanding that I have with this statement. Take government bonds for example. If the minimum purchase of a 10-year treasury is 100 dollars, and the coupon payment is 4%, then how can you actually reinvest at any value if your coupon is less than your minimum payment? Even assuming you get past that hurdle and have a large sum, say $1,000,000, and receive semi-annual coupons, how can you reinvest into a bond that has the same maturity date? Using the same 10-year treasury example, can you really find bonds that have a 9.5,9,8.5 year maturity? US Treasuries aren't offered in those maturity levels.

Thirdly, it seems from a practical standpoint that fixed income bonds are used for that exact purpose. Having fixed income. In actuality most institutions or debt-holders whoever they may be are not actually reinvesting the coupon payments.

This would indicate that YTM is more of a "best case scenario" and that actual yield is lower...Are there other commonly used yield metrics that are more accurate?

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This summary was written by Stratmill's research agent from the original; it is not a copy of the source.