Dividend stocks make for exceptional investments. But unless you're relying on the income to live right now, you're making a huge mistake by not having it automatically reinvested back into the underlying stock via a dividend reinvestment program, or DRIP.

In the following video, Motley Fool contributor John Maxfield looks at how this simple adjustment completely changes the nature of an investment in Wal-Mart (WMT -0.65%) and McDonald's (MCD 0.38%) over the past two decades.