Fewer than 20 companies have paid higher dividends for at least 50 straight years, and only five offer safe, high-yield dividends of at least 3%. Each of the five high-yield dividend stocks below is a member of the dividend kings list and pays a safe dividend with continued dividend growth extremely likely. 

Companies that have managed to pay and grow dividends for such a long time typically have strong competitive advantages, generate consistent free cash flow, maintain conservative balance sheets and put shareholders first.

We own several of these high-quality dividend stocks in our Top 20 Dividend Stocks and Conservative Retirees dividend portfolios as well. Let's take a look at these high-yield dividend stocks that have rewarded investors with at least 50 consecutive years of dividend growth. 

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1. Vectren Corporation (VVC)

Vectren is a holding company for three operating utilities that provide energy delivery services to more than one million natural gas and electric customers located throughout Indiana and Ohio. 

Vectren maintains construction relationships with regulators in its two states and expects to make infrastructure investments of about $2.2 billion from 2016-2020 to continue driving utility earnings growth. Overall, Vectren's utility operations are allowed a healthy 10.3% return on equity in 2016 and have achieved consistent rate base growth. 

The stability of Vectren's regulated utility operations has allowed the company to increase its dividend for 56 consecutive years, and management last boosted the payout by 5.3% in November 2015. Unlike many utility stocks, Vectren's outlook for growth is very healthy. The company expects earnings and dividend growth of 5%-7% per year through 2020, maintaining a safe dividend payout ratio near 60%.

This high-yield dividend stock offers a dividend yield of 3.2% and trades with a price-to-earnings ratio of 19.7, based on forward earnings estimates. 

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2. Procter & Gamble(PG) - Get Report

Procter & Gamble has been in business for 178 years and is one of the largest consumer packaged goods sellers in the world with more than $70 billion in revenue.

The company owns 21 billion-dollar brands, including Tide, Pampers, Bounty and Charmin. Its business is diversified across a number of recession-resistant categories such as fabric care, health care, grooming, and baby, feminine and family care, providing nice earnings stability. 

By maintaining heavy advertising spending and staying ahead of evolving consumer trends, Procter & Gamble has carved out very strong market positions. In its 10 product categories, the company is No. 1 in seven of them and No. 2 in the other three.

Procter & Gamble is one of our favorite blue-chip dividend stocks and has paid a dividend for an astounding 126 straight years since its incorporation in 1890. Very few companies have demonstrated such durability.

Procter & Gamble has raised its dividend for 60 consecutive years, and management most recently increased the company's dividend by just 1% in April 2016. The disappointing growth rate largely reflects the transformation P&G is undertaking to streamline and invest in its business in an effort to rejuvenate growth.

The company's payout ratio is also relatively high near 70%, but the dividend remains very safe given the stable nature of P&G's consumer staples products.

PG's shares sport a high-yield dividend of 3.2% and trades at a P/E of 22.8, based on forward earnings estimates. 

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3. Coca-Cola(KO) - Get Report

Coca-Cola is arguably the most iconic beverage company in the world and owns a portfolio of more than 500 brands, including 20 billion-dollar brands.

The company's durability is largely a result of its intensive marketing efforts and world-class distribution network, which consists of about 250 bottling partners that deliver Coca-Cola's beverages to 24 million customer outlets all around the world.

Coca-Cola began paying quarterly dividends in 1920 and has increased its dividend for 54 consecutive years, including a 6% boost in February 2016. The company is a member of the dividend aristocrats list given its inclusion in the S&P 500 index and minimum dividend growth streak of 25 years.

Despite stagnant demand for sparkling beverages and a dividend payout ratio near 70%, Coca-Cola's dividend growth has remained in the mid- to high-single digits in recent years.

Shares of Coca-Cola trade at a P/E of 23.9, based on forward earnings estimates, and offer a high dividend yield of 3%.

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4. Emerson Electric(EMR) - Get Report

Emerson Electric's roots date back to 1890 when the company began operations as a manufacturer of electric motors. Since then, Emerson has grown into a worldwide manufacturer of industrial and technical equipment such as valves, compressors, precision instruments, and sensors.

Emerson has been a great business for many years because it has focused on selling high-value equipment that represents a small proportion of an end product's total cost but is part of a mission-critical piece of functionality. Customers are happy to pay up for reliability and dependability.

Management is in the process of further strengthening Emerson by spinning off noncore assets to refocus the company on its highest margin, fastest-growing business segments, which are mostly focused on controlling industrial processes.

Emerson Electric's dividend has increased for nearly 60 years. Dividend growth has remained in the mid- to high-single digits in recent years, and the company's payout ratio near 50% provides plenty of safety and room for future growth.

Emerson Electric is a high-yield dividend stock that trades at a P/E of 17.7 based on forward earnings estimates. It offers a high dividend yield of 3.5%.

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5. Northwest Natural Gas(NWN) - Get Report

Northwest Natural Gas (NW Natural) has been in business for nearly 160 years and provides natural gas distribution and storage services to more than 700,000 residential, commercial and industrial customers located throughout Oregon and Washington.

Many investors are not familiar with this small-cap stock despite its high yield and consistent dividend growth, but NW Natural has grown to be the largest independent natural gas utility in the entire Pacific Northwest. The company maintains constructive relationships with regulators and operates in regions characterized by above-average customer growth and investments.

NW Natural maintains an A+ credit rating from Standard & Poor's and has a low-risk business profile because more than 90% of the company's revenue is from pure-play local distribution companies, which maintain the portion of the utility supply grid that's closest to end customers.

NW Natural's business stability and financial conservatism have enabled it to increase its dividend for 60 consecutive years. While the company has an admirable dividend growth streak, actual dividend growth has remained at less than 2% in recent years.

NWN's stock offers a high-yield dividend of 3.6% and trades at a P/E of 24.1, based on forward earnings estimates.

This article is commentary by an independent contributor. At the time of publication, the author was long EMR and PG and held no position in NWN, VVC, or KO.