Dividend investors would be wise to focus not just on a stock's current yield, but also on the long-term growth potential of its dividends. That's because strong businesses that consistently raise their dividend payouts reward shareholders with a steadily rising income stream that essentially equates to a raise every year. And, well, who doesn't like a raise?

But there are other reasons to value dividend growth so highly, and they're well supported by research. For instance, a study by C. Thomas Howard published in Advisor Perspectives found that for every percentage point a stock's yield rises, its annual return increases by 0.22 percentage points if it's a large cap, 0.25 if it's a mid-cap, and 0.46 if it's a small cap. Even better, Howard found that dividend-growing stocks outperformed dividend cutters by 10 percentage points per year from 1973 to 2010 and beat both flat- and no-dividend stocks. And the icing on the cake is that Howard showed that this outperformance came with a third less volatility. Higher returns, less volatility-induced stress, and a steadily growing income stream -- what's not to love?

With that in mind, here are five stocks that have grown their dividends by more than 25% over the past year.

Source: S&P Capital IQ.

Amgen is a biotechnology company that discovers, develops, manufactures and markets human therapeutics based on advances in cellular and molecular biology. Major products include Neulasta and Neupogen, used to stimulate the production of white blood cells; Enbrel, an inhibitor of tumor necrosis factor that plays a role in the body's response to inflammatory diseases; and Aranesp and Epogen, which stimulate the production of red blood cells. Amgen currently has a four-star ranking on CAPS and offers investors a 1.7% yield.

Corning produces and sells specialty glasses, ceramics, and related materials worldwide. Its products are used in everything from flat-screen TVs to optical fiber to biosensors for drug research. And its Gorilla Glass technology is used in smartphones, tablets, and touch-enabled laptops. Corning currently sports a five-star rating in CAPS and is yielding 2.7%.

US Bancorp is one of the largest bank holding companies in the country, and it offers a diversified suite of financial services such as lending, depository, cash management, capital market, trust, and investment management services. US Bancorp currently sports a four-star rating in CAPS and is yielding 2.5%. Fools may also find it interesting that Berkshire Hathaway -- led by legendary investor Warren Buffett -- recently increased its investment in US Bancorp by more than 27%.

Coach is a marketer of fine accessories and gifts for men and women. Its product offerings include handbags, women's and men's accessories, footwear, outerwear, business cases, sunwear, watches, travel bags, jewelry, and fragrance. Fools have given Coach a four-star rating in CAPS, and its stock is yielding 2.5%.

Cummins designs, manufactures, distributes, and services diesel and natural gas engines, electric power generation systems, and engine-related component products, including filtration and emissions solutions, fuel systems and controls, and air handling systems. CAPS participants have awarded Cummins with the highest five-star rating, and the company is paying out a 1.9% dividend yield.

The Foolish bottom line
Had you invested in these companies a year ago, you would have enjoyed total dividend increases ranging from 25% to nearly 30%. That level of growth would provide a substantial boost to just about any investor's dividend income. But more important to investors today is to identify the companies that will grow their dividends substantially in the years ahead. If you're interested in hearing about some excellent companies that are likely to boost their dividends from this point forward, I'd like to offer you a brand-new free report from The Motley Fool's expert analysts called "Secure Your Future With 9 Rock-Solid Dividend Stocks." Today I invite you to download it at no cost to you. To discover the identities of these companies before the rest of the market catches on, you can access this valuable free report by simply clicking here now.