In retirement, investors must figure out how to generate enough income without a job while also ensuring that they don't outlive their income stream. The best retirement stocks to buy in 2020 (or any other year), then, assuredly must be dividend-paying ones.

Receiving regular dividends reduces an investor's dependence on the market's fickle price swings to make ends meet. Whether or not the market rises or falls in 2020, a portfolio of quality businesses can continue delivering predictable, growing dividend income.

Compared to many fixed-income investments, dividend stocks also can generate higher current income in today's low-interest-rate environment, growing their payouts each year to help preserve one's purchasing power. Dividend stocks, like other equities, provide meaningful long-term price appreciation potential as well.

Research firm Simply Safe Dividends published an in-depth guide about living on dividends in retirement here. However, a key component to this strategy is finding the best retirement stocks that can deliver safe dividends and grow in value over time.

On that note, these are the 20 best retirement stocks to buy in 2020. The 20 stocks on this list appear to have safe dividends, yield between 3.5% and 6.9%, and have solid potential to continue growing their payouts in the long term.

Flowers Foods

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People have to eat, and Flowers Foods (FLO, $21.69) has served this basic need since 1919. The baked goods company sells a variety of breads, buns, snack cakes and rolls. While bread is a very mature product category, Flowers has some of the most relevant brands.

The company's Dave's Killer Bread is the nation's largest organic bread brand, and Canyon Bakehouse is the fastest-growing gluten-free bread brand in the country. Flowers also owns Nature's Own, the No. 1-selling loaf bread brand; Wonder Bread, which enjoys 98% consumer awareness; and TastyKake, among others.

Consumers continue buying these products in good times and bad, making Flowers a recession-resistant business - a common trait among many of the best retirement stocks to buy. The company's sales slipped just 2.6% during the Great Recession. And FLO shares only lost 2% while the S&P 500 slumped 56.8% during the 2007-09 bear market. Add in dividends, and Flowers actually eked out a positive total return of 0.8%.

Flowers' dividend has been reliable, too. The company has raised its payout each year since it began distributing dividends in 2002. With an investment-grade credit rating, excellent cash flow generation, and a reasonable payout ratio of roughly 80%, Flowers' dividend seems likely to remain a safe bet.

Crown Castle International

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Crown Castle International (CCI, $134.53) is the largest provider of shared communications infrastructure in America, with a portfolio of more than 40,000 cell towers, about 70,000 small cell nodes and over 75,000 route miles of fiber.

The assets are leased to wireless service) and AT&T (). These firms place their equipment on Crown Castle's towers and small cells so they can beam their signals to mobile devices used by consumers and businesses.