By Ilie Mitaru, PCWorld

Thirty-five percent of Americans own smartphones, according to a study conducted this spring by the Pew Internet & American Life Project. It found that 83 percent of U.S. adults have cell phones, whether “smart” or not. Forty-two percent of those cell phone owners have a smartphone, which translates to 35 percent of all adults.

For business owners, the data drives home the importance of having a robust mobile strategy. A Yahoo study last year found that two-thirds of smartphone users will use the device to shop, which includes browsing, reading reviews, and comparing products. A complementary Google study found that 40 percent of smartphone users will check out product reviews before purchasing.

These numbers are a year old, and have undoubtedly increased since their publication. Still, they do point to the tremendous boom in smartphone usage, both in ownership and their influence on purchasing decisions.

The Pew survey, in addition, found that 59 percent of adults in households earning $75,000 or more have smartphones, while 48 percent of those with a college degree do.

Other factors, such as mobile payments, will further accelerate smartphone adoption. For example, Square allows merchants to use their smartphones as traditional credit card swipers. Even more liberating for the mobile user are electronic wallet services. With Google’s eWallet, you don’t need your cards; simply use your phone’s near field communication technology (NFC)–not yet widely available–to transmit your payment info to any participating vendor. The eWallet is currently released on a test basis to a handful of U.S cities.

Along with mobile payments are a slew of companies developing location-based services in an effort to draw you into their businesses. Facebook and Google both have their Places feature, which allows users to check into a location and publish your presence there to their networks. Foursquare, which has registered over a half-million merchants, entices smartphone users to check in with exclusive deals and other games.

All these platforms can be used freely, you don’t any special mobile app or even an mobile-optimized website. Simply register and begin offering deals.

Among smartphone owners in the Pew study, 87 percent have access to the Internet or email on the handset, while 68 percent get online with the devices every day. A comparatively smaller 25 percent of owners said they use smartphones to access the Internet more than on a computer.

Android remains the most popular platform, with Apple’s iOS second and RIM’s Blackberry coming in third.

And the age bracket most likely to own a smartphone, at 58 percent, was those between 25 and 34 years old. While 49 percent of those between the ages of 18 and 24 own smartphones, 44 percent between 35 and 44 do. These age groups are golden for advertisers.

If you don’t have a mobile strategy yet, either due to time or budget constraints, the easiest way to fake one is with a solid social media presence. Google+, Facebook, and Twitter all have robust mobile functionalities, so by building out a presence on one or all of these platforms, you automatically give your potential customers an easy way to find and connect with you. Even if your website isn’t mobile compatible yet, get involved with a social network. (And if you’re building a business website from scratch, make sure it can be read on mobile phones.)

The Pew survey comprised of 2277 respondents, of which 1522 interviews were conducted by landline phone and 755 interviews were conducted by cell phone.

Ilie Mitaru is a culture and business journalist and an occasional entrepreneur. Follow him@iliemit.