When advisors invest your money in several Dimensional funds, they give you access to thousands of equity and fixed income securities in more than 40 countries, a level of diversification that is extremely difficult for individuals to obtain on their own.

Stock prices in markets around the world fluctuated dramatically for the week ending August 27. On Monday, August 24, the Dow Jones Industrial Average fell 1,089 points—a larger loss than the “Flash Crash” in May 2010—before rallying to close down 588. Prices fell further on Tuesday before recovering sharply on Wednesday, Thursday, and...

Volatility is back. Just as many people were starting to think markets only ever move in one direction, the pendulum has swung the other way. Anxiety is a completely natural response to these events. Acting on those emotions, though, can end up doing us more harm than good.