Source: ADP.

Many dividend investors focus exclusively on high yields from their stocks, choosing to let lower-yielding dividend payers go untouched. Yet that would lead you to leave out stocks like Automatic Data Processing (NASDAQ:ADP), which has a nearly 40-year track record of dividend growth under its belt. Even though ADP's 2.3% yield doesn't look like anything special, the company's commitment to dividend growth has only been eclipsed by the pace at which its share price has climbed in recent years. Let's take a look at three reasons why ADP deserves to be called a top dividend stock.

1. ADP's dividend has risen steadily for decades.
It's easy to assume that a low yield means that a company hasn't truly committed itself to dividend growth. Even though ADP has earned a prestigious spot among the Dividend Aristocrats with its 39 consecutive annual dividend increases, even membership in that elite group doesn't necessarily mean that the pace of dividend growth over the long run is anything special.

For ADP's part, though, the company has done a good job not just in raising dividends but in giving meaningful and significant increases to shareholders. For the past three years in a row, ADP has made dividend increases of around 10%, and most investors expect ADP to announce a similar-sized increase later this month.

ADP Dividend data by YCharts

Granted, ADP hasn't always been as generous with its dividend increases. During the financial crisis, ADP made only minimal dividend increases, preserving capital as it went through a tough time in its core business. Yet even at that point, ADP didn't give up on making big boosts, and with quarterly payouts having almost quadrupled in just the past decade alone, dividend investors can count on sustained growth in the quarterly payments they receive on their ADP shares.

2. Employment is back on track, giving ADP growth opportunities.
Automatic Data Processing provides outsourcing services to its clients, with a particular emphasis on payroll. As a result, ADP often does best when the economy has the most positive momentum, as a strong economy encourages more hiring and puts more businesses in a position in which they can afford to look outside their own walls to get help managing administrative functions like payroll.

Over the past five years since the financial crisis, ADP has seen impressive earnings growth, and positive employment numbers have a lot to do with those improved results. As you can see below, the 2008 recession really hit ADP's earnings hard, and the sluggish recovery that followed initially limited the company's ability to bounce back.

ADP Net Income (Annual) data by YCharts

But gradually, unemployment levels have started falling back down toward more normal levels. In particular, positive conditions in key areas of the U.S. economy, such as the energy industry, have driven labor-market strength in certain areas of the country. More broadly, a generally favorable view toward the overall economy has improved business confidence and encouraged employers to consider hiring new people and tapping ADP for more of its services.

Obviously, ADP will face business cycles in the future. But one sign of the strength of its dividend is that ADP has weathered short-term storms before without losing its dividend-paying resolve, and that doesn't appear likely to change anytime soon.

Source: ADP.

3. ADP has tapped a key market that its competitors haven't been able to penetrate.
One of ADP's biggest strengths is that it targets some of the largest companies in the world to provide its services. In general, ADP has focused its efforts on big employers, and while it hasn't completely ignored mid-sized and small businesses, rivals Paychex (NASDAQ:PAYX) and Intuit (NASDAQ:INTU) have suites of services that target smaller-sized employers more directly.

Having large-company exposure makes ADP more stable during good times, but it also threatens to make it less nimble when opportunities to tap into broader employer markets arise. Moreover, as Paychex broadens its own target audience, ADP will repeatedly have to demonstrate that it's the best option for businesses of all sizes.

Automatic Data Processing isn't the best-known company in the U.S., but it's among the best dividend stocks investors could choose. With a history of strong business growth as well as a solid commitment to returning capital to shareholders, ADP should continue to be a top dividend stock well into the future.