You've probably heard of the S&P 500. Most people have. It’s the "market," right? Well, not exactly. If you only own the big guys, you are missing a massive chunk of the American economy that’s quietly humming along in the background. That’s where the Dow Jones US Total Completion Index comes in. It’s a mouthful of a name, honestly. But basically, it’s the index for everything else.
Think of the US stock market as a giant party. The S&P 500 or the Dow Jones Industrial Average are the celebrities at the VIP table. They get all the press. They have the most money. But the Dow Jones US Total Completion Index represents everyone else in the room—the mid-sized companies, the scrappy small-caps, and the firms that are actually growing fast because they aren't already trillion-dollar behemoths.
If you’re trying to build a "total market" portfolio, you can’t just buy the big names and call it a day. You need the completion. It's in the name for a reason.
What is the Dow Jones US Total Completion Index anyway?
Let’s get technical for a second, but not too boring. This index is designed to represent all US-headquartered equity securities with readily available price data, minus the stocks that are in the S&P 500. It’s a subset of the Dow Jones U.S. Broad Stock Market Index.
Imagine you have a giant pie representing every single public company in America. You take a huge knife and cut out the 500 biggest slices. What’s left on the table? That’s the Dow Jones US Total Completion Index.
It’s a float-adjusted market capitalization-weighted index. That’s just a fancy way of saying that the bigger a company is within this "non-S&P" universe, the more it affects the index’s price. But since the "Big Five" or "Magnificent Seven" aren't here, the weight is spread out much more thinly across thousands of stocks.
We are talking about roughly 3,000+ components.
Why do people even track this?
Most investors use it to fill the gaps. If you work for a company that offers a 401(k), you might see an option for an "Extended Market Index Fund" or a "Completion Fund." Usually, those funds are tracking either this index or its main rival, the S&P Completion Index.
They do this because sticking only to the S&P 500 means you have zero exposure to the "middle class" of the stock market. When small caps rally—which they often do when interest rates start to settle or when the domestic economy is buzzing—the S&P 500 might stay flat while the Dow Jones US Total Completion Index takes off like a rocket. It’s about not putting all your eggs in the Apple and Microsoft basket.
The weird relationship between Completion and the S&P 500
It’s a bit of a symbiotic dance.
When a company in the Dow Jones US Total Completion Index gets big enough and successful enough, it gets "promoted." S&P Global (the folks who run the S&P 500) might decide to add that company to the big index. At that point, the stock is removed from the completion index and moves into the S&P 500.
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It’s almost like a minor league baseball team. The completion index is where the future stars live. You get to own them while they are still growing. By the time they hit the S&P 500, a lot of the "easy money" has already been made.
Take a look at Tesla. Years ago, before it was the titan it is now, it lived in the extended market world. If you only held an S&P 500 fund back then, you missed that initial, insane vertical climb. By the time it joined the S&P 500 in late 2020, it was already a giant.
Is it riskier than the big stuff?
Honestly, yeah. It usually is.
Small and mid-cap companies are more sensitive to the local US economy. They don’t always have the massive cash reserves that a company like Alphabet or Berkshire Hathaway has. If a recession hits hard, these "completion" companies might struggle to get loans or keep the lights on compared to the blue chips.
But risk and reward are siblings.
- Volatility: You’ll see bigger swings here. On a bad day, the Dow Jones US Total Completion Index might drop 3% while the S&P 500 only drops 1.5%.
- Diversification: On the flip side, because it holds thousands of stocks, you aren't reliant on the success of just one or two tech giants.
- Correlation: These stocks often move differently than the mega-caps. Sometimes the big tech stocks are selling off because of some weird international regulation, while the mid-sized US construction companies in the completion index are doing just fine.
How to actually invest in it
You can’t "buy" an index directly. You have to buy a fund that mimics it.
Most people use the Vanguard Extended Market Index Fund (VEXAX for the mutual fund version, or VXF for the ETF). This fund is basically the poster child for the "completion" strategy. It tracks the S&P Completion Index, which is nearly identical in philosophy to the Dow Jones US Total Completion Index. Fidelity also has options like the Fidelity Extended Market Index Fund (FSMAX).
If you are a "Boglehead" or follow the total world indexing philosophy, you might just buy the Vanguard Total Stock Market ETF (VTI). That ETF basically combines the S&P 500 and the completion index into one single wrapper. It’s the "set it and forget it" move.
Real world performance: A reality check
Don't let anyone tell you that small caps always outperform. They don't.
In fact, for a huge chunk of the 2010s and early 2020s, the Dow Jones US Total Completion Index actually lagged behind the S&P 500. Why? Because we were in a "winner-take-all" economy. The biggest tech companies were growing so fast and were so dominant that they squeezed the life out of the smaller guys.
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But markets move in cycles. There have been decades where the completion index absolutely crushed the large caps. From 2000 to 2010—the "lost decade" for the S&P 500—small and mid-caps were one of the few places you could actually make money.
If you think the "Magnificent Seven" are getting too expensive or "bubbly," the completion index is your primary alternative. It’s where the value often hides when the big names get overpriced.
Sector weights: It’s not all tech
One thing you’ll notice if you dig into the Dow Jones US Total Completion Index is that it looks very different under the hood.
The S&P 500 is incredibly heavy on Information Technology. It’s basically a tech index at this point.
The completion index? It’s much more balanced. You’ll find a lot more Industrials, Financials (especially regional banks), and Healthcare (like biotech startups). It feels more like the "real" economy—the companies that build the roads, manage the local hospitals, and make the physical products we use every day.
What most people get wrong about "Total Market" funds
A lot of investors think that if they own a Total Market fund, they have a 50/50 split between big and small companies.
Nope. Not even close.
Because these indices are market-cap weighted, the S&P 500 companies make up about 80% to 85% of the total market’s value. The Dow Jones US Total Completion Index makes up the remaining 15% to 20%.
Even though there are thousands more companies in the completion index, they are so much smaller that they don't move the needle as much as a single bad day for Apple might. If you really want "small cap" exposure to change your life, you sometimes have to "overweight" the completion index—meaning you buy more of it than the market naturally suggests.
The "January Effect" and other quirks
There’s this old market lore called the January Effect. The idea is that small-cap stocks (the ones that dominate the Dow Jones US Total Completion Index) tend to outperform in January.
The theory is that investors sell their losers in December for tax-loss harvesting, which drives the prices down. Then, in January, they buy back in. While the effect isn't as reliable as it used to be, it highlights how these smaller stocks are driven by different psychological and tax-related factors than the massive stocks that pension funds hold forever.
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How to use this information right now
If you’re looking at your brokerage account today and realizing you only own an S&P 500 fund (like VOO or SPY), you are essentially betting that the 500 biggest companies in America will always be the best performers. History says that’s rarely true forever.
Here is how to actually put the Dow Jones US Total Completion Index to work for you:
Check your current exposure. Look at your 401(k) or IRA. If you see "Large Cap" everywhere, you're missing the completion. You might want to add a 10% to 20% allocation to an extended market fund to capture that broader growth.
Don't panic during volatility. Understand that the completion index is "jittery." It will bounce around more than the S&P 500. If you can't stomach a 20% drop in a bad month, keep your allocation small.
Watch the interest rates. Smaller companies often carry more debt relative to their size. When the Federal Reserve cuts rates, the Dow Jones US Total Completion Index often reacts more positively than the mega-caps because their borrowing costs drop significantly.
Stop looking for the "next big thing" in the news. By the time a stock is all over CNBC, it’s probably already huge. If you want to own the "next big thing" while it's still a "medium-sized thing," you need to be in the completion index.
Rebalance once a year. If the completion index has a massive year and the S&P 500 stays flat, your 20% slice might become a 30% slice. Sell some of the winners and move them back into the big caps. This forces you to buy low and sell high—the only real rule in investing that matters.
The Dow Jones US Total Completion Index isn't flashy. It doesn't have the "cool" factor of a concentrated AI portfolio. But it is the backbone of a diversified strategy. It’s the insurance policy that ensures you aren't left behind when the market's leadership inevitably shifts away from the giants of today toward the innovators of tomorrow.