I took my first investing class as a teenager, and one moment stands out in my memory. A fellow student asked the instructor, a stockbroker, about dividends.

"Dividends?" he asked. "I'm trying to make my clients wealthy. You don't do that waiting for tiny checks in the mailbox every quarter."

Even then, I had enough horse sense to know he was wrong. Paying attention to dividends is exactly how you become wealthy over time.

Wharton professor Jeremy Siegel made a wonderful discovery in his book The Future for Investors. The greatest long-term returns typically don't come from the most innovative companies, or even companies with the highest earnings growth. They come from companies that happen to crank out dividends year after year. Simply put, since the 1950s, "the portfolios with higher dividend yields offered investors higher returns."

Market commentary regularly centers around price gyrations, yet dividends have historically accounted for more than half of total returns.

Reinvest those dividends, and it's even greater. Take ConAgra Foods (NYSE: CAG) for example. Since the early 1970s, ConAgra's share price has increased 7,700%. But add in reinvested dividends, and total returns jump all the way to 28,000%:

Source: Capital IQ, a division of Standard & Poor's.

There's no ambiguity here: Over time, ConAgra's share appreciation alone has paled in importance to the power of its reinvested dividends. The results are similar for other food companies such as J.M. Smucker (NYSE: SJM) and Hormel (NYSE: HRL); reinvested dividends skew both companies' total long-term returns dramatically higher. If you're a long-term shareholder, don't worry about daily share wobbles. Devote your attention those dividend payouts, and your commitment to reinvest them.

And how do ConAgra's dividends look? At 4%, its current yield is well above the market average. Dividends have been paid every quarter since at least 1977. While free cash flow has fluctuated wildly in recent years, management stressed its commitment to dividends on a recent conference call. "We remain committed to a top-tier dividend payout," CFO John Gehring said. "We know that a healthy dividend is important to many of our investors."

To earn the greatest returns, get your priorities straight. What the market does is less important than what your company earns. What your company earns is less important than how much it pays out in dividends. And what it pays out in dividends is less important than whether you reinvest those dividends.