Private Real Assets vs. HY Bonds

Kaplan answer explanation:

“Private real assets (e.g., timber) have a high or strong potential to fulfill capital growth, income, and diversification from public equities. Public real assets (energy, metal, etc.) have a high potential to diversify public equities, but not to provide income or capital growth. High-yield credit has a high potential for income, a medium for diversifying public equities, and limited capital growth opportunity.”

Why does high-yield credit have limited capital growth opportunity compared to private real assets? I’m assuming it is because rates usually can only fall to 0 or a negative rate close to 0 so there’s always somewhat capped capital appreciation whereas most other assets can increase in value without restriction theoretically.

The risk premiums in the discount rate will likely never go away, so the YTM will never go low enough to pick up meaningful capital gains.