Fast growth and massive sales don't always align in business. These 10 companies, however, have managed to have both, increasing already eye-popping revenue figures at a rapid rate over the past three years. In 2017, they brought in a combined $43.6 billion, more money than the GDP of Estonia. Below, check out the biggest revenue drivers of the Inc. 5000.

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10. Transportation Insight

2018 Inc. 5000 rank No. 3010 Three-year growth 134% 2017 revenue $1.9 billion

This logistics business helps distributors, retailers, and manufacturers optimize and manage their supply chain, whether they need to transfer goods by cargo ship across the world or analyze shipping costs and pay bills. The Hickory, North Carolina-based company has been honored on the Inc. 5000 list of America's fast-growing private companies a total of 10 times.

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9.  Insight Global

2018 Inc. 5000 rank No. 4973 Three-year growth 58% 2017 revenue $1.9 billion

This Atlanta-based company provides IT staffing for large and midsize companies in the U.S. and Canada, with a focus on the defense, aerospace, and health care industries. The 10-time Inc. 5000 honoree places 35,000 temporary-to-permanent workers at companies across North America each year.

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8. Pinnacle Group

2018 Inc. 5000 rank No. 2064 Three-year growth 216% 2017 revenue $2.1 billion

Based in Dallas, Pinnacle Group is a 12-time Inc. 5000 honoree. The company offers vendor management, payroll services, and technical administrative staffing to major companies around the world. Founder Nina Vaca started the business 21 years ago.

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7. SRS Distribution

2018 Inc. 5000 rank No. 3546 Three-year growth 106% 2017 revenue $2.2 billion

A four-time Inc. 5000 honoree, SRS Distribution is a national wholesale roofing-products distributor that serves independent roofing contractors across the country. The McKinney, Texas-based company has made more than 30 acquisitions since its 2008 founding and now has over 220 locations in 42 states. 

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6. Armada

2018 Inc. 5000 rank No. 4204 Three-year growth 81% 2017 revenue $2.9 billion

This Pittsburgh-based company manages supply chains, warehousing, and distribution for companies from all types of industries in the U.S. and Europe. Armada, founded in 1890 as a meatpacking company, pivoted to transportation logistics and software in the early 2000s. 

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5. DriveTime

2018 Inc. 5000 rank No. 4341 Three-year growth 77% 2017 revenue $3.2 billion

This online used-car retailer and financing company helps customers find and buy vehicles from 140 dealerships across the United States. A four-time Inc. 5000 honoree, DriveTime was founded in 2002 and is headquartered in Tempe, Arizona. With 6,000 employees, it's one of the largest used-car businesses in the U.S.

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4. Endeavor

2018 Inc. 5000 rank No. 3439 Three-year growth 111% 2017 revenue $3.5 billion

Endeavor is a Beverly Hills, California-based entertainment, media, and sports conglomerate run by legendary talent agents Ariel Emanuel and Patrick Whitesell. It comprises the entertainment agency formerly known as WME-IMG, as well as mixed martial arts organization UFC and advertising agency Droga5.

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3. Carahsoft Technology

2018 Inc. 5000 rank No. 4226 Three-year growth 80% 2017 revenue $4.1 billion

This 10-time Inc. 5000 honoree, founded in 2004, offers IT solutions to the U.S. government. Based in Reston, Virginia, the contractor provides agencies including the Department of Homeland Security with software from vendors like Symantec, Dell EMC, and SAP. Carahsoft is one of the fastest-growing IT government solution providers in the nation.

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2. Allied Universal

2018 Inc. 5000 rank No. 1318 Three-year growth 363% 2017 revenue $5.3 billion

Helmed by CEO Steve Jones, the Santa Ana, California-based security and janitorial services company has 150,000 trained employees who work at 20,000 offices and sites across the U.S. This is the eighth year Allied Universal has been on the Inc. 5000.

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1. Prime Therapeutics

2018 Inc. 5000 rank No. 1288 Three-year growth 372% 2017 revenue $16.4 billion

Based in Eagan, Minnesota, this six-time Inc. 5000 honoree manages pharmacy benefits for health plans, employers, and government programs, including Medicare and Medicaid. More than a million Medicaid members use Prime Therapeutics' pharmacy benefit management services.