If you invest, and especially if you're approaching or already in retirement, two measures of Modern Portfolio Theory are worth understanding: alpha and beta. Most investors focus on returns. Fewer understand whether those returns were actually earned efficiently, relative to the risk taken to achieve them. That's exactly what alpha and beta help reveal.
Let's Start With Beta
Beta measures how sensitive a portfolio is to movements in a reference benchmark, most commonly, the S&P 500.
Here's a simple example: if your portfolio has a beta of 0.60, that means a 1% move in the benchmark has historically been associated with roughly a 0.60% move in your portfolio, on average. A beta of 1.20 means a 1% market move has historically been associated with roughly a 1.20% move in your portfolio.
Why does this matter? Because many investors assume their portfolio is more conservative, or more aggressive, than it actually is. Beta gives you a clearer, more objective picture of your portfolio's actual sensitivity to the market.
Now Let's Talk About Alpha
Alpha is sometimes described as your portfolio's "bang for your buck." More precisely, it measures the portion of your portfolio's return that is above, or below, what would have been expected given its level of market sensitivity.
In other words: alpha isn't just about what your portfolio returned. It's about whether that return was justified by the risk you took to get there.
Consider this example: if two portfolios each returned 10%, but one had a beta of 1.0 and the other had a beta of 0.60, the second portfolio delivered the same return with substantially less sensitivity to the market. That doesn't necessarily mean it experienced less overall volatility, but it's an important distinction worth understanding.
Why This Matters Even More in Retirement
For investors who are still in the accumulation phase, short-term market swings are easier to ride out. Time is on your side.
But once you retire and begin taking regular, meaningful withdrawals from your portfolio, consistency becomes increasingly important. Major market declines early in retirement, while withdrawals are also occurring, can have an outsized and lasting impact on how long your money lasts. This is often called sequence-of-returns risk.
That's why many retirees benefit from examining not just what their portfolio has returned, but how much market sensitivity it carries, and whether those returns were commensurate with that exposure. Alpha and beta together can help answer both questions.
What Should You Do With This Information?
Alpha and beta are just two data points, but they can reveal a lot about whether your portfolio is actually built for your goals and risk tolerance, or simply the one that was put together at some point and never revisited.
If you'd like help examining these characteristics and determining whether adjustments may make sense for your situation, reach out to a member of the SKG Team today!