Despite numerous market corrections during my investing career, I have been able to go about my life and not panic at the market's volatility. That's because my portfolio is made up of stocks that tend to hold up better than the broader market in periods of elevated stress.

A core holding in my portfolio that has made this possible is the supplemental insurer Aflac (AFL -0.41%). For example, while the S&P 500 index has fallen 9% year to date on news of increasing inflation and economic turmoil related to Russia's invasion of Ukraine, Aflac's stock has actually risen 5% so far in 2022. Despite Aflac's recent strong price performance, the stock is still a buy for investors seeking stability in a market currently fraught with uncertainty.

Here are four reasons why Aflac is a good buy right now.

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1. Aflac consistently outperforms analysts' expectations

When Aflac reported its fourth-quarter earnings on Feb. 2 for the period ending Dec. 31, the company exceeded the average analyst forecast for both revenue and non-GAAP (adjusted) diluted earnings per share (EPS). 

Aflac recorded $5.43 billion in revenue during the fourth quarter, which was an 8.1% year-over-year decline in revenue. But that total still managed to beat analysts' prediction of $5.24 billion in sales for the quarter. How did Aflac surpass the analyst revenue consensus for the seventh quarter out of the past 10? 

Two key factors led to a year-over-year decline in revenue for Aflac in the fourth quarter.

First, the COVID-19 pandemic negatively affected revenue in both the U.S. and Japan (where it mainly operates). Total U.S. revenue still edged 0.1% higher to $1.6 billion during the quarter. A 1.3% decline in U.S. net earned premiums due to fewer face-to-face sales was more than offset by an 8.2% increase in adjusted net investment income for the quarter. In Aflac's Japan segment, a 16.8% increase in adjusted net investment income wasn't enough to offset the 4.3% decline in net earned premiums (also due to limited face-to-face sales) recorded in Japanese yen in the fourth quarter. Total Japan revenue fell 8.5% year over year to $3.6 billion for the fourth quarter.

Second, Aflac's revenue was negatively affected by unfavorable foreign currency translations. That's because Aflac earns a significant portion of its revenue in Japanese yen and then converts those yen into U.S. dollars. And the average exchange rate worsened 8% in the fourth quarter, to 113.70 yen-to-the-dollar from the year-ago period average exchange rate of 104.57.

While revenue was pressured in the fourth quarter, Aflac's profitability held strong due to fewer claims resulting from the effects of the pandemic. As a result, the company's adjusted diluted EPS surged 19.6% higher year over year to $1.28 for the fourth quarter. This narrowly topped the analyst consensus of $1.26, which marked the 20th consecutive quarter that Aflac was able to do so.

2. Interest rate hikes will provide a lift for the business

Aflac delivered a solid fourth quarter to its shareholders. And with the Federal Reserve set to raise interest rates this year, Aflac will be a beneficiary since part of its $143 billion investment portfolio is invested in U.S. bonds. This will allow the company to purchase higher-yielding bonds and provide a lift to its investment income going forward.

3. Dividend growth has accelerated in recent years

Aflac has raised its dividend paid to shareholders annually for 39 consecutive years, which makes the stock a well-established Dividend Aristocrat. For a stock with such a lengthy track record of upping its dividend, a reasonable investor would expect dividend growth to be slowing down.

But Aflac's most recent 21.9% increase in its quarterly dividend per share to $0.40 per share per quarter was the largest percentage increase since its 20% dividend hike in 2008. Why was the board of directors confident enough to hand out a massive dividend bump to its shareholders? And can Aflac's inflation-beating dividend growth continue?

For one, Aflac's dividend payout ratio in 2021 was only 22.2%. This gives the company room to work with in terms of dividend increases. Second, analysts anticipate that Aflac's earnings will grow in the mid-single-digits annually over the next five years. Those two factors should allow healthy dividend growth to persist for the foreseeable future. Best of all, that growth will come on top of a market-topping 2.6% dividend yield.

4. Aflac is trading at an appealing valuation

The final reason to consider buying Aflac is its valuation. Aflac's forward price-to-earnings ratio of 10.9 is moderately lower than the insurance industry average of 12.4. Given its quality, I believe Aflac deserves to trade at a slight premium to its peers.

Aflac also appears to be cheap based on the fact that its price-to-book (P/B) ratio of 1.2 is below its 13-year median P/B ratio of 1.4. Since Aflac's fundamentals look to be robust, it looks like a good buy for long-term investors.