An index fund is a fund that simply invests in all of the stocks in a market. So, for example, an index fund might invest in every single stock or almost every single stock in the U.S. market, it might invest in every single stock abroad, or it might invest in all of the bonds that are out there. And you can make a perfectly fine investing portfolio that mixes equal parts of all three of those.

Market risk is like taking a plunge into a cool pool ... a lot of people are finding out right now what their risk tolerance is.

While it is probably a poor idea to own actively managed funds in general, it is truly a terrible idea to own them in taxable accounts... taxes are a drag on performance of up to 4 percentage points each year... many index funds allow your capital gains to grow largely undisturbed until you sell... For the taxable investor, indexing means never having to say you're sorry.

No one in his right mind would walk into the cockpit of an airplane and try to fly it, or into an operating theater and open a belly. And yet they think nothing of managing their retirement assets. I've done all three, and I'm here to tell you that managing money is, in its most critical elements even more demanding than the first two.

Do the math. Expect catastrophes. Whatever happens, stay the course.

The typical fund company services 401k plan participants in the same way that Baby Face Nelson serviced banks.

When it comes to fund managers and market strategists, this year's hero usually turns into next year's zero.