Since the end of 2009, we've been hearing about the "lost decade" of the '00s or the aughts. Sounds sort of romantic in a dark way, like holing up in a secret place and doing something mysterious when nobody knows where you are. But of course, it refers to the ten-year period, beginning in 2000, when stock market investors actually lost money. Isn't that what we promised would never happen? An entire decade of loss?

It certainly happened to investors who put all their money in large-cap U.S. equities. Every dollar invested in the Standard & Poor's 500 index on December 31, 1999, was worth 75 cents ten years later. But it didn't happen to those with discipline and a plan. And I'll bet it didn't happen to your clients.

Of course, the idea of a lost decade conjures up the mishaps and misfortunes of Japanese investors who suffered through their own bubble while U.S. investors smugly looked on, believing that it couldn't happen here. During the Japanese asset price bubble from 1986 to 1991, real estate and stock prices grew hugely inflated. That bubble didn't burst so much as slowly collapse in a process that lasted more than a decade. Stock prices seemed to bottom in 2003 but the global financial crisis in 2008 brought them even lower.

David Falkof, an analyst at Morningstar, describes the past decade in the U.S. like this:

"It began with the Internet boom and bust, ended with a roaring housing and credit market bubble that imploded catastrophically, featured a mutual fund trading scandal and the rise of ETFs in between, and left most equity fund investors with little to show for their pains on December 31, 2009. During all the turmoil, a lot of investors lost their faith in some big funds, broad diversification, and sober stewardship."

Where do we go from here? Some Americans worry that the U.S. will suffer through the same sort of malaise that Japan has not yet managed to escape. Others argue that everything is fixed now; the global economy has been salvaged and returned to the track. Some of them say that it's even better than that: The stock market returns 10% a year, on average, over time, so doesn't that mean we have a lot of good news and good returns ahead of us?

I called Don Phillips, managing director at Morningstar, to see what he thought about the lost decade. As I suspected, he was annoyed with the whining and grumpiness. "It really gets under my skin," he says, "this assumption that it's up to the markets to do the heavy lifting and that you don't have any responsibility for saving." Don never loses his faith in the market. He sticks to his rules and continues to make regular investment contributions and rebalancing. Last year was no different for him.

But he says he was surprised to see that some financial advisors lost faith in that system. At the Financial Planning Association's national conference and at its retreat, he saw market-timing presenters giving their pitches to rooms full of advisors.

"I never thought I would see market timing pitches to a serious audience of financial planners and also see them seriously considered," he says. "Financial planners are such caring people, and it must have been difficult for them to see clients suffer [through the market chaos]. But not one fund has ever put together a successful record based on market timing."

What can the profession do then? Several observers say the decade provided more evidence that investors must be more geographically diversified and more diversified across asset classes.