Houston isn't just all about energy Health care and retail are at top of area's job numbers; United Airlines also a leader

Movers arrange the furniture in the new pediatric inpatient unit, Monday, June 3, 2013, in Houston. This is for the chron 100 and the story on the biggest employers. MD Anderson is number two on the list and it's growing. ( Karen Warren / Houston Chronicle ) less Movers arrange the furniture in the new pediatric inpatient unit, Monday, June 3, 2013, in Houston. This is for the chron 100 and the story on the biggest employers. MD Anderson is number two on the list and ... more Photo: Karen Warren, Staff Photo: Karen Warren, Staff Image 1 of / 17 Caption Close Houston isn't just all about energy 1 / 17 Back to Gallery

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If you ask most folks, Houston is an oil and gas town. But when it comes to which companies have the most employees, health care and retail have energy beat.

The biggest companies in Houston, as measured by the number of employees, are health care institutions; consumer-service providers, including grocery stores and restaurants; and United Airlines. Only four companies in the top 15 are energy companies, according to the Chronicle's survey of biggest employers.

Topping that voluntary list is Memorial Hermann Health System with 21,000 employees. (Wal-Mart Stores has been the biggest in previous years, but the giant retailer no longer provides employment data for individual cities.)

Some of Memorial Hermann's growth stems from its expansion into suburban areas. In April, it announced plans to build a campus in Pear-land that will include adult and pediatric primary care, sports medicine and other specialists and a 24-hour emergency room.

The "convenient care center" is scheduled to open later this year, while a 64-bed hospital, the eventual centerpiece of the new campus, is scheduled to open in 2015.

Memorial Hermann also announced it would break ground next year on a six-story tower at its hospital in Katy.

Memorial Hermann's CEO and president, Dan Wolterman, credits the mathematics of population growth. For every 1,000 new residents, a certain number will need medical services.

"Anything outside of Beltway 8 is just exploding," said Wolterman, who is looking to the area between Beltway 8 and the Grand Parkway for the bulk of the hospital's growth. At the same time, there is growing demand inside Loop 610 in areas such as the Heights, Midtown and Uptown.

Wolterman also credits its efforts to build a stronger brand and improve the hospital's reputation among potential patients which, in turn, has fueled the need for more employees.

The University of Texas M.D. Anderson Cancer Center is No. 2 on the list with 19,486 employees.

Tom Burke, executive vice president and physician-in-chief for M.D. Anderson, credits its growing network of partnerships with providers such as St. Luke's and Christus to provide outpatient cancer care in four key suburban areas: Katy, The Woodlands, Sugar Land and Clear Lake.

Patients in those suburban neighborhoods can stay close to home and avoid the parking and traffic problems at the Texas Medical Center when they need routine lab work and chemotherapy treatments, while they remain patients of M.D. Anderson's main campus.

M.D. Anderson has also expanded its specialty cancer care - such as head, neck and breast - at its suburban clinics as well as running the cancer program at Harris County Health System's Lyndon B. Johnson General Hospital.

Patients want to see their medical specialists and surgeons at one time and in one place, Burke said. That way they can meet for conferences and get their treatment plans.

While hospitals and other medical providers aren't typically considered base industries because they tend to focus on treating local residents rather than generating money from outside the metro area, that's not the case with some of the specialty health care centers affiliated with the Texas Medical Center.

M.D. Anderson gets patient referrals from all over the state and the nation for its sophisticated treatment, so it's considered part of Houston's base economy, said Bill Gilmer, director at the Institute for Regional Forecasting at the University of Houston.

It also keeps money here at home because if M.D. Anderson were not in Houston, area residents with difficult-to-treat cancers would likely travel to Baltimore for treatment at Johns Hopkins University or to the Mayo Clinic in Rochester, Minn., for treatment. UTMB Health - No. 11 on the list of the largest employers - is also part of the base economy because of all the treatment it provides to the prison system in Texas, Gilmer said.

But grocers are strictly local. No one is going to drive in from Dallas to shop at H-E-B or Kroger.

He said United Airlines is part of Houston's base economy because it sells to the entire world.

United, Houston's fourth-largest employer, this spring showed off renovations at Bush Intercontinental Airport's Terminal B, which the airline uses for its United Express regional flights. The $97 million investment features larger passenger lounges and more space devoted to food, beverage and retail. The first 15 gates are already in use, with 15 more to open by year's end.