On Jan. 31, 1990, the very first McDonald's (NYSE:MCD) opened in Moscow. The move was hailed as the beginning of the end of the Cold War. But just as importantly for investors in the company, the store's opening was proof that demand was sky-high for the company's presence.

Not surprisingly, shareholders have been richly rewarded since then. Their returns total 1,740% since that blistery January morning, outpacing the S&P 500 by a wide margin.

Screen Shot

A look inside of a Moscow McDonald's location. Photo: Adam Baker, via Flickr

But the stock market is a forward looking beast, and investors should focus far more on what the company could do in the future, than what is has accomplished in the past.

Perhaps it is a harbinger of things to come, then, that Russian authorities have closed four McDonald's locations in Moscow over the past month. While this is officially the result of "sanitary issues", many believe it has more to do with strains international relations following the upheaval in Ukraine.

As you'll see below, this is just one, of many, problems facing the company. How will this affect McDonald's stock, and its dividend? Read below to find out.

McDonald's stock's most important metric
Though there are still opportunities for McDonald's to grow its brand internationally, most investors today are attracted to the stock because of its dividend. And when it comes to dividends, there's no metric more important than free cash flow. After all, it is from a company's free cash flow that its dividend is paid.

Here's a look at how McDonald's free cash flow situation has fared since 2009.

McDonalds Stock & Its Dividend | Create Infographics

As you can see, McDonald's has been able to grow its free cash flow between 2009 and today, but that growth came to a screeching halt in 2012. In fact, between 2011 and today, the company's free cash flow has increased by just 1.3% per year.

Another trend for investors to be aware of is that between 2009 and 2011, the company used roughly 59% of its free cash flow to pay out its dividend. Since then, the payout ratio has averaged 72%. Although the increase in payout ratio has benefited those who held shares prior to 2012, it raises a red flag for future investors. Higher payout ratios mean that the company has less room to grow the dividend, and less safety should business erode over time.

Why is business slowing?
To get an idea for why business is slowing, one only need look at how McDonald's is viewed by today's society. What was once a symbol for cheap, convenient, and tasty food is now a paragon of all that's wrong with the Western diet.

The company's same-store sales -- the second-most important metric to watch -- during 2014 bears this out.

McDonalds Same-Store Sales | Create Infographics

There are two big takeaways here. First, the company's locations in emerging markets (APMEA) have typically offset any weakness in Europe or at home. However, safety concerns regarding McDonald's suppliers in China have caused a significant dip over the last few months. That will likely be resolved, but has caused a lot of short-term pain.

For long-term investors, the far more concerning figure should be the fact that same store sales have consistently shrunk in America during 2014. This is McDonald's most mature market, and this trend may be a sign of things to come for investors who plan on keeping the company, and its stock, in their portfolio for decades to come.

McDonald's stock: buy or sell?
If you believe that McDonald's can grow itself internationally, redefine itself as a more health-conscious location for customers -- or some combination of these two -- then it's safe to say that free cash flow will continue to increase in the future, and the dividend will be relatively safe.

If, however, you think the long-term trends toward healthy eating will cause a slow death to McDonald's and its ilk, this is a dividend you should be wary of. Unless the company is able to increase same store sales, it will not be able to grow free cash flow over the long run. That means a lower dividend payout, and not much fun for investors.

Brian Stoffel has no position in any stocks mentioned. The Motley Fool recommends McDonald's. 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.