Being an intelligent investor means looking at a business from every angle. This means understanding why a stock could fall as well as why it could rise. But, let's be honest, the fun part is predicting why it will grow.

While I can't foresee the future, I do believe there are three reason's supplemental insurer Aflac's (NYSE:AFL) stock price could rise in the short, medium, and long-term.

Short term: Japan Post 
Among the most exciting short-term developments at Aflac is its strengthening relationship with Japanese banking, insurance, and post office conglomerate Japan Post. The combination of Aflac's industry leading cancer insurance with Japan Post's massive distribution channels has already started paying dividends. According to CEO of Aflac Japan, Tohru Tonoike, Japan Post is accountable for the largest growth in cancer insurance sales. 

Moreover, management suggested that the two companies are discussing expanding their alliance from Aflac's insurance being sold in 10,000 locations to 20,000 by the end of 2015. 

Aflac has also recently launched two new cancer-related products. One of which will be sold exclusively through Japan Post, and the other through Aflac's other established pipelines. While the product with Japan Post is critical, I will be keeping an eye on the second offering. As management suggested, the new cancer insurance will "offer better pricing at many age groups." The 20-40 age group is a widely underpenetrated market for Aflac and it could be a huge opportunity if this product can connect with a younger audience. 

If Aflac can continue to leverage its relationship with Japan Post, while improve its distribution among age groups, sales and the company's stock price would likely see a boost.

Medium term: Rising interest rates 
By focusing on medical and life insurance, Aflac receives payments from consumers for years, or even decades, before they ever payout anything in claims. Aflac creates interest income by investing the buildup in customer premiums also referred to as the insurance "float." 

Over the first nine months of 2014, Aflac earned $2.5 billion in investment income. What makes this truly impressive is that interest rates in Japan and the U.S. are at all-time lows, and Aflac is receiving a 2.8% yield on investments in Japan and 5.9% from the U.S. 

If interest rate were to rise, Aflac would be able to invest at higher yields and create more investment income. Unfortunately, with the Bank of Japan -- which serves a similar purpose as the U.S. Federal Reserve -- still attempting to grow inflation it doesn't seem likely this will happen any time soon. The good news, however, is that the Federal Reserve is currently predicting they will increase U.S. interest rates sometime in mid-2015.

The increases will likely happen slowly, but any meaningful increase in rates would improve Aflac's ability to generate greater returns and would likely have a positive impact on the company's stock price.

Long term: Stronger Japanese economy 
With 75% of Aflac revenue coming from Japan, the company's long-term growth will depend on the health of Japan's economy. 

AFL Chart

On the surface, the immediate future of Japan looks pretty dim. The nation is battling low inflation, the population is in decline, and for its size, Japan is the most indebted country in the world. But, there is a silver lining.

The Bank of Japan has suggested it will do whatever it takes to improve the country's outlook -- which will mostly include printing a ton of money. Similar to the U.S., the BOJ has been making huge purchases of government bonds and similar assets. This is done to keep interest rates low and increase consumer spending and inflation.

Because there has only been moderate progress to this point, on Oct. 31, the BOJ suggested they will not only continue on this path, but will be increase bond purchases between 10 trillion and 20 trillion yen -- or $91 billion-$181 billion, respectively. This will increase annual spending to 80 trillion yen, or $725 billion.

It's hard to say whether the additional bond purchases will have the intended affects, but it is promising to see that the BOJ is willing to do whatever is necessary. However, if it does work -- and Japan starts making sustainable improvements -- the better economy would create huge upside for Aflac and its stock price.

Dave Koppenheffer has no position in any stocks mentioned. The Motley Fool recommends Aflac. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.