It’s no great surprise that the sustainability of retirement income from a diversified portfolio is driven by the returns that the portfolio generates over time. And to the extent that stocks are the driver of long-term returns, the valuation of the markets at the beginning of retirement has a significant impact on long-term portfolio returns throughout retirement.
However, the reality is that bonds often comprise a significant portion of the retirement portfolio, and they do play at least some role in long-term retirement income sustainability. As a result, to the extent that interest rates are especially high – or in today’s environment, are unusually low – yields too can play a non-trivial role in long-term expected portfolio returns.
And the historical data really does suggest that at today’s nominal yields, long-term bond returns are likely to be suppressed, even if rates normalize in the coming years. In fact, extremely low starting bond yields, and the potential subsequent impact on prices if/when/as rates rise, are so impactful that it would be reasonable to reduce long-term 30-year real bond returns by as much as about 2%.
Notably, the eventual climb to higher yields does ultimately result in higher nominal yields in the future. Even from an extremely low starting base, long-term real government bond yields have never been worse than 1%/year over a multi-decade time horizon. Nonetheless, given that the historical real return of government bonds has been closer to __%, the potential to be several hundred basis points lower, for decades to come, is a substantial impact that should be reflected in a retiree’s prospective financial plan.