Quick, what’s the difference between a market-cap-, equal- and price-weighted stock market index? Fortunately, if you’re not sure, our friends at Dimensional Fund Advisors just published an excellent piece on this very subject. We invite you to read it here, but here’s our overview.

If you think of a market as a big box, there are several ways each stock that belongs in that box might “weigh in” to help fill it:

Market-Cap Weighted – If we fill a market box according to each stock’s market capitalization (share price multiplied by shares outstanding), the stocks with the biggest market caps (e.g., Apple stock –  AAPL) weigh the heaviest, or occupy the most space, as Dimensional depicted here:

Equal Weighted – If, each security is instead given equal space in the box regardless of its market-cap, an equal-weighted market will look more like this:

Price Weighted – As described in this recent New York Times piece (which may require a subscription to access), the Dow Jones Industrial Average is the only popular index that uses price weighting, where the highest-priced stocks take up the most space. (Almost everyone agrees, price-weighting is pretty arbitrary, especially since the Dow tracks only 30 U.S. stocks to begin with. But as the world’s first and oldest index, the venerable Dow essentially gets to do as it pleases.)

So what does all this mean to you as an investor? As Dimensional’s illustrations depict:

• If you were to invest all of your money in a single market-cap-weighted index fund, you’d end up holding a much heavier allocation to large-cap stocks, be they value or growth.
• If you were to invest everything in an equal-weighted index fund, you’d end up holding more small-cap stocks than would otherwise be warranted by their cap-weighted presence in the total market.

Now, here’s where things get a little complicated, so bear with me. At first glance, you might conclude you’d be best off investing in an equal-weighted index fund, to capture more of the higher expected small-cap value premium. After all, that’s where the biggest small-cap value “blob” appears, right?

Not so fast. First, we’ve got to remember that an index is just a theoretical collection of stocks. When an investor or fund manager seeks to replicate an index by placing actual trades on those stocks, they run into real-life trading constraints. This is especially so when tracking an equal-weighted index, where far more frequent trading is likely to be the norm.

Put plainly, keeping up with the evolving components in an equal-weighted index can get very expensive, very fast.

Dimensional explains:

“[U]sing a systematic and purposeful approach that takes into consideration real-world constraints is more likely to increase your chances for investment success. Considerations for such an approach include things like: understanding the drivers of returns and how to best design a portfolio to capture them, what a sufficient level of diversification is, how to appropriately rebalance, and last but not least, how to manage the costs associated with pursuing such a strategy.”

Which brings us back to evidence-based investing as we know it. Want to know more? Here’s a past post on index- vs. evidence-based investing. Or just give me a call to continue the conversation.

End notes:
Exhibit 1: For illustrative purposes only. Illustration includes constituents of the Russell 3000 Index as of December 31, 2016, on a market-cap weighted basis segmented into Large Value, Large Growth, Small Value, and Small Growth. Source: Frank Russell Company is the source and owner of the trademarks, service marks, and copyrights related to the Russell Indexes. See Appendix (on page 3) for additional information.

Exhibit 2: For illustrative purposes only. Illustration includes the constituents of the Russell 3000 Index as of December 31, 2016 on an equal-weighted basis segmented into Large Value, Large Growth, Small Value, and Small Growth. Source: Frank Russell Company is the source and owner of the trademarks, service marks, and copyrights related to the Russell Indexes. See Appendix (on page 3) for additional information.

In my early years with Hill Investment Group, here’s a question I would see in people’s puzzled faces almost every time I mentioned fund manager Dimensional Fund Advisors:

“Dimensional who?”

With the continued shift to evidence-based investing, the question has become something more like this:

“Who’s this ‘Dimensional Fund Advisors’ I keep hearing about?”

The name may be more familiar these days, but with their nerdy academic underpinnings and publicity-shy approach, it’s still a challenge to explain exactly what makes the firm tick. As the firm’s Investment Research Committee Chair Ken French says, “People at Dimensional care much more about getting the right answer than defending their answer.”

Fortunately, Dimensional has created a great new piece entitled “Inside Dimensional 2017.” Equal parts science, philosophy, and intellectual horsepower, it offers a fascinating tour through the firm’s inner workings – including an entire section dedicated to its “Data Dogs” and their use of computers to revolutionize the implementation of finance for investors.

Let us know if you would enjoy a behind-the-scenes peek at Dimensional’s people and culture, and we’ll gladly send you a copy of “Inside Dimensional.”

Sometimes, it’s admirable to persevere against slim odds and sometimes not – such as if you’re trying to pick the next winners among actively managed funds. Think you can identify which ones will not only survive the next few years but also outperform their peers? Dimensional took a look at this question and found the likelihood is somewhere in the range of slim odds to fat chance.

Want to know more about how to interpret this chart – and invest accordingly? Give us a call.