Why Momentum Investing Works – A Wealth of Common Sense

Momentum investing has a reputation problem. Say “I buy what’s been going up” at a dinner party and someone will inevitably clutch their pearls, whisper “bubble,”
and slide your bread basket to the other side of the tablejust in case your strategy is contagious.

And yet, momentum is one of the most researched, most persistent return patterns in markets. Even Ben Carlson at A Wealth of Common Sense calls himself
“a huge fan” of the momentum factorespecially for diversificationwhile also admitting it’s misunderstood and can be awkward to implement in real life
(turnover and taxes tend to be the party crashers). Momentum feels backward because it sounds like “buy high, sell higher,” but it’s more precise than that:
it’s about riding trends that tend to persist in the short to intermediate term before the long-term forces of mean reversion show up and change the vibe.

What Momentum Investing Actually Means (and What It Doesn’t)

Momentum is not “YOLO into whatever is trending on social media”

Real momentum investing is rules-based. It systematically tilts toward securities that have outperformed recently and away from those that have underperformed.
“Recently” is usually measured in months, not minutes. If your “strategy” depends on your mood, a meme, or your friend’s cousin’s barber, that’s not momentum
that’s improv comedy with your savings.

Two flavors: relative strength and trend following

• Cross-sectional (relative) momentum: compare assets to one another. Example: buy the “winners” among U.S. stocks (or sectors) and underweight
  the “losers,” based on trailing performance (often ~12 months, skipping the most recent month).
• Time-series momentum (trend following): compare an asset to itself. Example: hold an index if its recent trend is positive; reduce or avoid it
  if the trend is negative. This concept shows up in many managed futures/trend strategies.

Practitioners often describe momentum as “cut losses, let winners run.” That’s not just a motivational posterit’s a behavioral antidote.
Humans are famously bad at doing this consistently (we love holding losers “until they come back” and selling winners “so we don’t lose the gain”).
Momentum flips that instinct on purpose.

The Evidence: Momentum Shows Up… a Lot

The modern momentum conversation in stocks took off with academic research showing that stocks with strong past returns tended to keep outperforming over the next
several months. The classic “sort winners and losers” results became a cornerstone of factor investing research, and momentum later appeared as a key ingredient
in widely used multi-factor models.

Momentum isn’t a single “one weird trick”

Momentum has been documented:

• Across stocks (winners tend to keep winning for a while, losers tend to keep lagging).
• Across markets globally (not just a U.S. quirk).
• Across asset classes in trend-following form (equity indexes, rates, commodities, currencies).

Importantly, momentum is not “free money.” It’s a compensated pattern that can come with unpleasant periodssometimes very unpleasantespecially around sharp
market turning points.

So… Why Does Momentum Investing Work?

There isn’t a single explanation that everyone agrees on, but three ideas show up repeatedly. Think of them as three suspects in the same mystery novelsometimes
one is guiltier, sometimes they’re all in on it.

1) Investors underreact (at first), then overreact (later)

New information doesn’t get fully priced in instantly. Companies report earnings, guidance changes, industries shift, and it often takes time for the crowd to
adjust beliefs. Early on, prices may move “not enough” (underreaction). As the narrative spreads, more investors pile in, analysts update models, and the trend
can feed on itselfsometimes pushing too far (overreaction). That “gap in time” before mean reversion is exactly where momentum tends to live.

2) Real-world constraints slow down “smart money”

Even if some investors spot mispricing, they don’t have unlimited capital, patience, or career risk tolerance. Professional managers face tracking-error limits,
committee oversight, and the uncomfortable truth that being right early can look identical to being wrong. If exploiting momentum requires standing apart from a
benchmark (or shorting losers), it can take time for enough capital to act on it.

3) Momentum may be “paid” for crash risk and nasty tail events

Momentum strategies can suffer sharp drawdownsparticularly when markets snap back quickly after prolonged stress. Research on “momentum crashes” points to a
common setup: a rough market period followed by a rapid rebound in what had been the biggest losers. If a momentum portfolio is positioned against those losers,
it can get hit hard when the comeback rally arrives.

Momentum’s “Bad Hair Days”: The Part People Forget to Mention

Momentum works over long horizons, but it doesn’t work all the time. It tends to struggle during abrupt reversalswhen leadership flips fast.
If you only learn about momentum from a chart that goes up and to the right, you’re learning about momentum the way people learn about hiking from Instagram:
suspiciously free of sweat, bugs, and regret.

Momentum crashes: why reversals can hurt

A classic momentum pain point is the sharp rebound after a deep drawdown. Former laggards can surge, and a momentum strategy that had been avoiding/shorting
them may take losses quickly. This doesn’t mean momentum “stopped working.” It means momentum has a specific weakness: sudden regime changes.

Whipsaws: when trends fake you out

Trend-following versions of momentum can also get “whipsawed”entering a position, getting stopped out, then watching the trend resume without you. That’s the
cost of trying to be disciplined when the market is being a little… dramatic.

How Momentum Gets Implemented in the Real World (Without Turning Your Life Into a Trading Desk)

Momentum sounds simple“buy winners, sell losers”but implementation matters. The difference between “a robust process” and “a chaotic mess” is usually a small
set of practical choices: measurement window, rebalance frequency, diversification, and friction control (taxes, spreads, and turnover).

Common momentum building blocks

• Signal definition: Many models use trailing 12-month returns and ignore the most recent month (to reduce short-term reversal noise).
• Rebalancing cadence: Monthly or quarterly rebalancing is common. Faster isn’t automatically betterfaster can mean more trading costs.
• Portfolio breadth: Holding a diversified basket of “winners” tends to reduce single-stock blowups.
• Risk controls: Position limits, volatility scaling, or trend filters can help keep the strategy from becoming an emotional rollercoaster.

ETFs and factor products: convenient, but mind the frictions

Momentum factor ETFs can provide exposure without building a do-it-yourself ranking engine. The tradeoff is that momentum tends to be higher turnover than many
other styles, which can increase trading costs and reduce tax efficiency in taxable accounts. Even “low-fee” products can quietly pay a price through turnover.
That’s why Carlson noted he wasn’t impressed with many retail momentum offeringsoften due to cost or tax efficiency.

Taxes and turnover: the unsexy, unavoidable reality

Momentum’s biggest practical enemy is friction. More trading can mean more realized gains, and short-term gains can be taxed differently than long-term gains.
In the U.S., the holding period matters for whether gains are short-term (one year or less) or long-term (more than one year). Also, frequent trading can raise
the odds of accidental tax pitfalls (like wash sales when harvesting losses).

None of this means “don’t use momentum.” It means: if you use momentum, do it with your eyes open, and try to match the tool to the account type and the
investor’s ability to stick with it. (Educational note: this is not personalized financial adviceconsider discussing decisions with a trusted adult/guardian and
a qualified professional.)

Why Momentum Can Diversify a Portfolio

One of momentum’s most appealing traits is that it doesn’t always win and lose at the same time as other factors. Value and momentum have often behaved
differently across cycles. When value is struggling, momentum may be thriving (and vice versa). That imperfect relationship can help a blended portfolio feel
less like it’s powered by a single engine.

Translation: momentum may not make your portfolio “always up,” but it can make the ride less dependent on one style working perfectly foreverbecause no style
gets to be the main character in every market scene.

Common Misconceptions (and the Quick Fixes)

“Momentum is just chasing performance.”

Momentum does use past performance, but it does so systematically and usually over intermediate horizons. “Chasing performance” is what happens when
someone abandons a plan after it underperforms and buys whatever just had a great year because it feels safe. Momentum is a process; chasing is a panic response.

“Momentum is day trading.”

Most academically studied momentum signals are measured over months, not hours. Day trading is a different sport with different skills, costs, and risks.

“If it’s well known, it can’t keep working.”

Some edges disappear when they become crowded. But momentum has persisted in research for decades, partly because it’s hard to stick with. Many investors bail
during the exact periods you’d need to endure to capture the long-term effect. In other words, the obstacle isn’t awarenessit’s behavior.

Putting Momentum to Work Sensibly

If you’re considering momentum exposure, the “grown-up” version is usually:

• Use a diversified approach rather than betting on one stock or one theme.
• Keep costs and turnover in mind, especially in taxable accounts.
• Expect occasional sharp drawdowns and reversalsplan emotionally as well as mathematically.
• Consider blending with other factors (like value or quality) rather than making momentum your entire personality.

Momentum isn’t magic. It’s a behavioral and structural phenomenon that markets keep serving up because humans keep being human and institutions keep being
institutional. The payoff, if there is one, goes to investors who can follow rules when their gut is yelling, “DO SOMETHING!”

Real-World Experiences Running Momentum (500+ Words)

Here’s the part most articles skip: what momentum investing feels like in practice. Not the backtest. Not the elegant academic chart. The lived
experience of following a rule set when the market is trying to narrate a different story every week.

First, momentum can be surprisingly boringright up until it’s not. In calm, trending markets, a momentum process often looks like “rebalance, make a few small
changes, go back to your life.” You’re not hunting for hidden gems in footnotes or arguing about whether a stock is “cheap” on forward earnings. You’re mostly
checking signals, updating allocations, and letting the trend do what trends do. That boredom is a feature. It reduces the temptation to overtrade and lets the
process compound without you interfering like an anxious stage manager.

Then comes the emotional whiplash: the month when leadership flips. A sector or group that’s been dominating suddenly faceplants. Meanwhile, the stuff you
avoidedbecause it was a disasterrips higher as if it got a motivational speech and a new haircut. Momentum investors often describe this as the “Wait… THAT
stock?” moment. The strategy is doing exactly what it promised: cutting what’s weakening and moving toward what’s strengthening. But your brain, which loves a
clean storyline, hates the messiness of transition periods.

A common experience is “selling too early” (even though you sold because the rules told you to). You exit a former winner after it breaks trend or falls out of
the top ranksthen it rebounds and you feel personally attacked by the candlestick chart. Momentum teaches a hard lesson: the goal is not to catch every last
penny of every move. The goal is to capture the middle of big, persistent moves often enough that the math works out over time. Missing some upside is normal.
Getting repeatedly chopped up is the cost of protection against bigger trend failures.

Another real-world feature: momentum can make you look wrong at exactly the wrong time. When markets reverse fast, your positioning may lagbecause momentum is
intentionally slow enough to avoid reacting to every wiggle. That lag is what helps during noisy markets, but it can sting during turning points. In those
moments, investors who don’t truly “buy in” to the philosophy are tempted to override the system. They add discretionary tweaks, change the lookback window,
or abandon the approach entirely. Ironically, the biggest behavioral risk isn’t the model being imperfect; it’s the investor trying to “fix” it mid-storm,
usually by doing the opposite of what long-term discipline would suggest.

Many momentum investors also learn to respect frictions. A backtest doesn’t complain about spreads, taxes, or trading costs. Real life does. People who run
momentum successfully tend to simplify: fewer rebalance dates, liquid instruments, clear rules, and an honest plan for taxes. They also learn that momentum is
not a personality test. You don’t need to evangelize it. You need to execute it, quietly, even when it’s temporarily unpopularbecause momentum, by design,
often feels uncomfortable when it’s working (buying what’s already up) and uncomfortable when it’s not (getting hit in reversals). The “skill” is sticking to a
process that isn’t always emotionally rewarding.

In short: momentum investing works best when you treat it like a durable system, not a highlight reel. The day-to-day experience is less about being clever and
more about being consistent. If you can handle the awkward monthsand not confuse temporary pain with permanent failuremomentum becomes less of a mysterious
factor and more of a practical way to harness the market’s tendency to move in trends.

Conclusion

Momentum investing works because market trends tend to persist long enough to be captureddriven by slow information diffusion, human behavior, and structural
constraints. It’s counterintuitive, it can be tax-inefficient if implemented carelessly, and it occasionally gets punched in the face during sharp reversals.
But for disciplined investors, momentum can be a powerful return driver and a useful diversifier alongside other approaches.