Unemployment rates are still trending near multidecade highs at 9.1%, but not everyone is feeling the effects of a sputtering economy. Paychex (Nasdaq: PAYX) surprised Wall Street (and me) by reporting fourth-quarter and fiscal 2011 results after the bell yesterday that more than exceeded some of the most optimistic estimates.

Keep in mind that Paychex is primarily a payroll-services company, so employment rates and customer retention play a significant role on determining its growth and bottom-line profitability. Based on Paychex's full-year report and fiscal 2012 guidance, the company has resounding told pessimists to "stuff it."

A look at these results from a full-year perspective shows that overall service revenue, which is the heart and soul of Paychex's business, grew by 5%. Payroll revenue grew by a modest 2%, but more importantly, checks per client rose by 2.1%, while customer-retention rates improved by 9% over last year. In short, fewer clients are going out of business, and the ones that remain in business are hiring. Either that's a resounding endorsement that the American economy is on the right track, or Paychex has an amazing ability to wisely choose its customers. I tend to believe in the former.

Even more impressive than its results was its guidance. The company anticipates service-revenue growth of 7% to 9% in 2012, boosted largely by a 12% to 15% expected jump in human-resources revenue. Profits are anticipated to be in line with current expectations, but the company's forecast implies revenue projections that should top the current forecast of $2.19 billion.

Still, some risks remain.

Is this unsustainable?
I want to see Paychex growing organically and through acquisitions, rather than relying on its investment income. But low interest rates are taking their toll on this segment of Paychex's business, resulting in a 13% decline in interest on funds in 2011 and an anticipated 12% to 14% drop in 2012. Luckily, this segment amounts to only 2% of Paychex's revenue, so I wouldn't raise the red flag by any means.

Besides, there's another concern that stands more at the forefront to me: the company's payout ratio. Paychex pays out a sizable dividend to shareholders -- currently north of 4%. In 2011, the company paid out 87% of its earnings in the form of a dividend, leaving little margin for error and little room for innovation. Its dividend stands leaps and bounds over rivals Automatic Data Processing (NYSE: ADP) and Insperity (NYSE: NSP), which yield 2.7% and 2.0%, respectively. But I'm concerned that its dividend payout may be unsustainable if the economy even moves moderately in the opposite direction. My advice would be to keep your eyes on that dividend payout ratio, which, at 87% is already dangerously high.

Taking names, writing checks
In all, this was another solid performance for Paychex. It was the third straight quarter of increased net income and the fourth quarter in a row of increased revenue. The company's numbers continue to defy a steadily high unemployment rate, and its dividend payout is enough to attract those looking for a moderate to high yield. Seriously -- what recession?

Would you take a chance on Paychex here? Share your opinion in the comments section below, and consider tracking Paychex with our free and easy-to-use watchlist service to keep up on the latest news in the payroll-services sector.

Fool contributor Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong. Motley Fool newsletter services have recommended buying shares of Automatic Data Processing and Paychex. Try any of our Foolish newsletter services free for 30 days. We Fools don't 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 that checks itself before it wrecks itself daily.