When it comes to university presence in research parks, the numbers are all over the map.

Purdue University has no university offices in its park, with minor exceptions. At Iowa State, up to 30 percent of the park's square footage can be university space.

At a typical North American research park, 14 percent of the tenants are university-related facilities, according to an October 2007 survey by Battelle for the American Association of Research Parks.

Here in Champaign, University of Illinois offices make up about 24 percent of research park tenants, including the Illinois Natural History Survey and the Illinois State Geological Survey. They consume from 9 percent to 27 percent of the park's total square footage (593,000 square feet), depending on how the space is defined.

"That's definitely not our goal to have a lot of university departments" in the park, said Avijit Ghosh, UI vice president for technology and economic development. Still, he is not opposed to the idea that UI offices and the research park sometimes make a good fit.

Ghosh said he would like to see more amenities at the UI park, including small retail shops and perhaps a coffeehouse along with ATM kiosks.

Mixed-use developments, with a strong university presence and on-site amenities, are the wave of the future, according to the association's study. North Carolina State University's Centennial Campus combines university and commercial space.

It's divided into "neighborhoods" focusing on different high-tech sectors, and some of its major colleges have relocated there.

Research park governance also varies, according to the study. About 43 percent of the parks surveyed are managed by a university or a university-affiliated nonprofit entity; only 6 percent are managed by a for-profit developer, the study said.

Many parks hire private developers on a case-by-case basis to construct new buildings, but only 15 percent reported using a private-sector master developer for the entire park, as the UI did. An even smaller percentage, 5 percent, are managed and financed by private, for-profit developers.

The reason some foundations and research parks like to bring in developers is to add "someone who brings in expertise in building property," said Eileen Walker, chief executive officer for the Association of University Research Parks.

The economic recession hasn't made a huge impact on the country's research parks, Walker said, but small startup companies may have trouble growing in the current climate.

Joe Hornett, chief operating official for Purdue's research park, said the park hasn't been hit by the recession as much as he thought it would. Park downsizing has been minimal, and he said there are no plans for businesses in the park to close or reduce staffing.

As for Wisconsin's research park, Greg Hyer, associate director of the park, said he's seen a deceleration, but startups are still launching in the incubator building there.

"Companies' expansions are slowing down, but we're not losing them," Hyer said.

Here's a look at how three Midwestern parks developed and their status this year:

Purdue University

Location: Main park in West Lafayette, plus three new campuses in Indianapolis, New Albany and Merrillville, Ind.

Year established: Founded in 1961 but didn't gain momentum until 1999, when the Purdue Research Foundation opened a state-of-the-art incubator facility, according to Joe Hornett, chief executive officer of Purdue Research Park. Then-President Steven Beering also openly promoted the idea of academics as entrepreneurs, and a series of covenants set aside land at the park for companies looking to foster a partnership with Purdue.

Structure: Run by research foundation created by the university in 1930.

Size: West Lafayette, 725 acres; Indianapolis, 78 acres; Merrillville, 386 acres; New Albany, 40 acres.

Employees: More than 3,500 across four parks.

Focus: A mix of large internationally recognized companies and startups along with a strong incubator facility.

Tenants: West Lafayette park houses 160 companies, including such notable names as C-SPAN Archives, Bioanalytical Systems Inc. (a pharmaceutical company) and Sikorsky Aircraft Division of United Technologies.

Occupancy: New buildings are constructed when existing facilities hit 80 percent occupancy. Main campus is filled except for recently opened 106,000 square feet, which was partially leased.

University offices: The foundation's partnership with the university does not include allocating research park space for university offices. The only university offices are technical assistance programs that provide technology services to businesses in the parks.

Iowa State University

Location: Ames.

Year established: 1987.

Structure: ISU Research Park Corp., nonprofit corporation overseen by a board of directors chosen by Iowa State University and the ISU Foundation.

Size: 230 acres.

Employees: Approximately 800.

Focus: Build, support and attract companies to help diversify the state's economy, according to Steven T. Carter, president of the park.

Tenants: Park hosts tech-based companies, from agriculture and biotechnology to materials science and human health, Carter said. It includes big-name companies such as Siemens and BASF that acquired smaller successful research firms or wanted to be closer to prominent ethanol market.

Occupancy: More than 50 companies.

University offices: The park allows 30 percent of its space to be used for university offices, but staying below the cap hasn't been a problem, Carter said.

University of Wisconsin

Location: Madison.

Year established: 1984.

Structure: Run by university-affiliated private research foundation.

Size: 255 acres.

Employees: Approximately 3,500.

Focus: Park doesn't spend time attracting Fortune 500 companies, instead concentrating on spinoff businesses from the university, said Greg Hyer, associate director for the park.

Tenants: Mostly science and technology companies with connections to the university. Park also includes 80,000-square-foot incubator with 30-plus companies, and mixed-use businesses such as a family dentist practice and a nonprofit organization dedicated to improving local public schools.

Occupancy: 36 buildings including Madison Gas & Electric Innovation Center and more than 110 companies.

University offices: The park includes some university offices such as the Master of Science in Biotechnology and the National Primate Research Center.