This is a guest post from Robert Brokamp of The Motley Fool. Robert is a Certified Financial Planner and the adviser for The Motley Fool’s Rule Your Retirement service. He contributes one new article to Get Rich Slowly every two weeks.

Stocks stink.

That’s something you hear a lot these days, and with good reason. The Standard & Poor’s 500 sits at around 1060, a threshold it first crossed in the beginning of 1998. In other words, that index of stocks in 500 industry-leading American companies — companies like ExxonMobil, Johnson & Johnson, Coke, and McDonald’s — has gone up and down a lot over the past 12 or so years, but has ended up in the same place where it started.

So you might think that if you invested $10,000 in the S&P 500 through something like the Vanguard 500 index fund back in the spring of 1998, you might still have just $10,000. But actually, you’d have approximately $12,000 — not great, but better than nothing.

How is that possible? Permit me to explain with a metaphor.

If money grew on trees
If money grew on trees...Let’s imagine that you could buy a plant that grew money. That would be one valuable shrub, so it wouldn’t come cheap. In fact, let’s say a plant that produced $2 a year costs a hundred bucks. Still, you buy a whole bunch of them because:

  1. Each one produces $2 today and will provide a little more money each year as the plant grows, perhaps $4 in a decade, and
  2. In the future, another gardener might pay you more than $100 each for these plants.

What do you do with the cash your plants are providing? Buy more money-growing flora, so you can use the greenbacks they produce to buy, yes, more plants. When the market decides that they’re worth more than $100, you get fewer of them. When the market thinks they’re worth less, you’ll be able to buy more.

By the time you retire, you’ll own a whole lot of plants and, as they mature, they’ll each produce more money each year — perhaps $10 or more apiece. You may opt to sell some when the market catches on and offers a price higher than what you paid. But even when you retire, you should still own many of these shrubs because you’ll need to harvest the cash to pay your bills.

Stalks for the long run
Okay, we all know that money doesn’t grow on trees. But most stocks pay dividends; plus, historically, over the long term those dividends increase. When you reinvest those dividends — as most people do — you’re automatically dollar-cost averaging (that is, buying more shares when prices are low and fewer when prices are high). You gradually accumulate more shares, which gradually pay bigger dividends, which are used to buy more shares, which pay bigger dividends…and so on.

The same goes for mutual funds that invest in stocks. In fact, let’s look at the real-life example of the aforementioned Vanguard 500, which attempts to mimic the performance of the S&P 500 at very low costs. (I own the fund myself.) Not every company in the S&P 500 pays dividends, but this will provide an illustration of how dividend reinvestment can pay off.

Had you invested $10,000 in the Vanguard 500 Fund on 31 March 1998, you’d have bought 97.84 shares, according to numbers provided to me by Vanguard. Over the subsequent year, the fund paid out $1.06 per share in dividend distributions.

Technical note: Mutual fund shares also pay out capital-gains distributions, but not as consistently. So, for simplicity’s sake, we’ll focus mostly on dividends.

Fast-forward to July 2010. You now have 121.15 shares — almost 24% more than you started with. That’s because you were accumulating more shares with all those fund distributions. But the news gets a little bit better. For the past year, the Vanguard 500 paid out $2.08 in dividend distributions. Over the past 12 years, the dividend almost doubled. Plus, you have 24% more shares paying that bigger dividend, which will buy more shares…well, you know the drill.

“Big deal!”
I know what you’re saying: “Making a 20% total return over 12 years is lame! I know this blog is called Get Rich Slowly, but that’s ridiculous.”

I agree. As I said in the title of this post, investing in stocks hasn’t been quite as bad — but it’s still been bad. In fact, the last decade or so has been the worst period for blue-chip U.S. stocks since 1926, including the period encompassing the Great Depression (according to data from Ibbotson Associates).

I bring all this up to illustrate a few points:

  • Indexes can be misleading. Stock barometers such as the S&P 500 and the Dow Jones Industrial average are price indexes; they just measure the change in prices of the underlying stocks, and don’t factor in dividends or their reinvestment. That’s unfortunate, because…
  • Over the long term, dividends matter. Historically, dividend reinvestment has accounted for approximately one-third of the total return of stocks. That said, yields on stocks are pretty low these days, which means stocks aren’t a great bargain. But for my long-term money (I don’t plan to retire for another 30 years) I’m betting that the 2% to 3% yield on a broadly diversified portfolio of stocks — along with some capital appreciation — will beat the alternatives, namely, low-yielding cash and bonds (though I own some of each for diversification’s sake). This brings us to our third, final, and perhaps most important point…
  • Don’t invest in just one type of plant stock. Over the past decade or so, large-cap U.S. stocks — the type you find in the S&P 500 — have been the just about the worst type of investment to own. Name another type of stock (small-cap stocks, international stocks, real estate investment trusts) and chances are, as a group, they beat the S&P 500. As I explained in this video (just in case you’re dying to hear my nasally voice or see my hair while it still exists) and touched on in this previous GRS article, a properly diversified portfolio holds stocks of all types, sizes, nationalities, and flavors, with bonds or cash thrown in to suit your risk tolerance or financial needs (e.g., a retiree should have five years’ worth of income that is expected to be covered by saving sequestered from stocks and in something super-safe, like cash, CDs, or short-term bonds).

I have no crystal ball. I don’t know whether U.S. stocks or international stocks or cash or plants will be the best-performing asset class over the next decade or few. If you think the stock market is a sucker’s bet, I’m not here to argue with you. Just taking a look at the Japanese stock market — which is still down 70% from its 1989 peak, despite being the second-biggest economy in the world — should make anyone appreciate the risks of stock investing.

But if you’ve decided to make stocks a part of your long-term portfolio, I think that understanding the role dividend reinvestment plays will give you a little more confidence to hang in there.

J.D.’s note: Robert’s “stalks for the long run” pun above made me die laughing. I realize it’s an esoteric personal-finance writer joke, but it’s a funny one all the same.

This article is about Investing