Middle market firms are defined as having revenues generally between $50 million and $1 billion. They create 40 percent of Gross Domestic Product and employ 40 percent of America’s workforce.

It’s those two percentages that have many analysts saying these companies form the backbone of the U.S. economy and represent a lifeline to economic recovery.

Despite the economic downturn, the middle market is thriving, which makes it the sector most likely to drive job creation domestically — middle market companies tend to hire more U.S. workers than any other firms.

The companies are geographically diverse and span every industry from retail to manufacturing. They represent brands that you are likely to encounter on a daily basis — from that morning cup of coffee to your iPhone case, to how you listen to the radio. There’s even a famous hot dog among them.

But only 20 percent of middle market companies are publicly traded, since the vast majority are owned by private-equity firms or families.

So how do you invest and seize on this growing sector? We’ve put together a list of middle market companies that trade on Wall Street and offer possible investing opportunities.

Note: The 2011 revenues (TTM) for each company are included in our list.

Posted 30 July 2012

Revenue (TTM): $616.7 million
Ticker: LNKD

If you’re looking to find new job leads or a potential business partner, you may have turned to the world’s largest online professional network to review one of the more than 90 million member profiles in over 200 countries. The company started out in the living room of co-founder Reid Hoffman in 2002 and is now growing at a rate of approximately two members per second.

Revenue: $245.2 million
Ticker: KYAK
Whether you’re booking a summer vacation or your next business trip, you might find yourself on Kayak.com.  The website and mobile applications allow travelers to research and compare information from hundreds of other travel websites in one display for free. It also provides multiple filtering and sorting options as well as travel management tools and services, such as flight status updates, pricing alerts and itinerary management. Once users find their desired flight, hotel or other travel products, Kayak sends them to their preferred travel supplier websites to complete their purchases.

Revenue: $656.8 million
Ticker: DNKN
Dunkin’ Brands combines perennial favorites — baked goods, coffee and ice cream. With approximately 16,800 points of distribution in nearly 60 countries worldwide, Dunkin' Brands is one of the world's leading franchisors of quick-service restaurants and includes Dunkin’ Donuts and Baskin Robbins. Dunkin’ Donuts is the largest coffee and baked goods restaurant in the world, with customers in 31 countries. Baskin Robbins is the largest chain of ice cream specialty stores.

Revenue: $66.2 million
Ticker: NATH
The hot dog eating contest is an annual tradition on the Fourth of July, but Nathan’s Famous is a growing business all year. The company began in 1916 as a hot dog stand on Coney Island. In 2011, customers bought more than 425 million Nathan’s Famous hot dogs at 40,000 food service and retail outlets across the country.

Revenue: $534.1 million
Ticker: WBMD
From minor scrapes to serious illnesses, consumers turn to WebMD as a leading provider of online health information. In 2011, the WebMD Health Network averaged 20 million users per month and 734 million aggregate page views.

Revenue: $251.6 million
Ticker: ZIPThe Zipcar founders sat in a café and decided to bring the European car-sharing idea to America. Now they run the world’s leading car-sharing network. Members (aka Zipsters) have 24/7 access to thousands of cars kept in reserved parking spaces in neighborhoods where they live and work. Zipcars are available by the hour or by the day through the company's reservation system, which is available by phone, computer or mobile device.

Revenue: $249.7 million
Ticker: SKUL

Large retailers such as AT&T Wireless, Dick’s Sporting Goods, Best Buy and Target carry Skullcandy headphones and audio accessories — with more than a thousand variations. But you probably recognize Skullcandy as a leading provider of stylish covers for your iPhone. In the first quarter of 2012, net sales increased 47.9 percent to $53.3 million.

Revenue: $304.1 million
Ticker: P
You’ve probably listened to the leading free Internet radio service. If so, you’re not alone — listeners spent 1.08 billion hours listening to Pandora during June 2012 — an increase of 77 percent from 605 million during the same period last year. Pandora counted 54.5 million active listeners at the end of June 2012, an increase of 51 percent over June 2011.

Revenue: $147 million
Ticker: BNNY
Pizza, pasta, and pretzels — all natural and organic. Annie’s has been selling products in packaged food categories (meals, snacks and condiments) for more than 20 years. Annie’s focuses on organic and natural alternatives to traditional convenience foods.

Revenue: $144.6 million
Ticker: WAGE
WageWorks administers tax-advantaged programs for employee benefits such as health and dependent care flexible spending accounts (FSAs), health savings accounts (HSAs) and commuter benefits, such as transit and parking programs.

Revenue: $729.4 million
Ticker: ETH

Ethan Allen manufactures and retails home furnishings and accessories. The company also offers home decorating and design solutions through retail networks. As of June 2011, it operated 147 design centers, and its independent retailers operated 140 others.