Alas, here's another word we seem to be using more and more these days. As Mr. Rewrite moves ever closer to lighting his virtual cigarettes with flaming dollar bills, he figures that he should spend a few seconds figuring out the correct use of free-fall/freefall/free fall.
There's no AP Stylebook entry, so Mr. Rewrite turned to the Webster's New World College Dictionary. It calls for free fall when referring to any unchecked, usually rapid, decline in value or stability. So use free fall when referring to Mr. Rewrite's 401(k) balance -- parentheses and no space on 401(k), by the way, per AP style.
There's more, however. The New World lists free-fall in reference to undergoing, experiencing or moving in free-fall, which Mr. Rewrite figures is what expert parachutists do. But the market isn't tumbling from an airplane, much as we feel like that's happening to us.