Source: American Tower.

According to a recent report from the United Nations, more than 4 billion people around the world remain disconnected from the Internet. This, in a nutshell, is why I believe American Tower (NYSE:AMT) is still a good investment.

There's a logic to the thesis. At some point, more of the world will have to be connected. Commerce depends on it, especially now that so many goods and services are shopped for, bought, sold, and traded online. Wireless is the fastest way to connect these people, and you can't have wireless without the towers that host the radios.

American Tower is the world leader in wireless towers. The company's global network includes 61,000 towers in 13 countries.

More sites are coming online soon. Earlier this month, American Tower completed its acquisition of Global Tower Partners for $3.3 billion in cash, which includes assuming $1.5 billion of outstanding debt. Sound like a lot? it is, but a closer look at American's cash flow statements show a history of generating more than $1 billion in cash flow after adjusting for working capital changes. More than enough to make regular debt payments.

Analysts see American Tower growing its earnings base by about 25% annually over the next five years. I think that's a minimum figure, if only because how disconnected the world is in relation to the population of the planet.

Meanwhile, here in the U.S., there are now more than 40 million tablets hooked up to either 3G or 4G wireless networks, researcher Strategy Analytics estimates. Handling the load created by so many mobile users probably means more access points, which, in turn, creates demand for American Towers' facilities. Or those of peers SBA Communications and Crown Castle International.

I'm not expecting a let-up anytime soon. Why? There's just too much business online. A June study published by eMarketer put total 2013 e-commerce sales at $1.2 trillion for the full year, with emerging markets such as Indonesia experiencing the fastest growth. The entire Asia-Pacific region is on track to produce $388 billion in online sales, up 23% year over year.

That number can keep growing. We just need American Tower to help us connect more of the world first. Think I'm wrong? Have a better idea? Tell us about it in the comments box below.