With its latest appointment, Sleep Number has become one of a handful of public companies in the United States where women make up the majority of corporate board members.

The Minneapolis-based company this week named Deborah Kilpatrick to its board, increasing the size to 11, six of whom are women.

Kilpatrick is the CEO of Evidation Health in San Mateo, Calif., a technology company that aims to harness data about everyday behavior to improve health outcomes.

Sleep Number said Kilpatrick's expertise is a good fit for the company, which uses data and technology to separate itself from competitors. Its SleepIQ technology feeds a comprehensive database of biometric data on consumer sleep habits from sensors embedded in Sleep Number mattresses.

Shelly Ibach, Sleep Number's president and CEO, said the board has been diligent about gaining diversity in experience, gender, ethnicity, age and tenure as well as expertise in different business areas.

"Deborah has considerable experience in the development and commercialization of digital health products," Ibach said. "In the end, it's still about finding the best candidate who can contribute to the ongoing shareholder value."

Research shows that companies with diverse boards also tend to perform better financially, said Joann Bangs, dean of the school of business and professional studies at St. Catherine University in St. Paul.

"Women directors are more likely to include a wider array of stakeholders in discussions, be more persistent in pursuing answers to difficult questions and work collaboratively, which leads to better communication," Bangs said. "But it takes multiple women on a board to achieve these results."

Equilar, which provides companies with tools for board recruiting and other matters, launched a Gender Diversity Index in February 2017 to track the representation of women on corporate boards. The group issues a quarterly report on boards' gender composition.

The latest report, tracking the Russell 3000 companies, found 16.9 percent of board members overall were women, up from 16.5 percent the previous quarter. In the report for the first quarter of 2018, one-third of new directors were women.

But female-majority boards are rare. According to Equilar, as of March 31 only 11 companies in their database had more women on their boards than men. Sleep Number becomes the 12th. Another 16 have 50/50 gender parity.

Sleep Number's board is chaired by Jean-Michel Valette. Other male board members are Daniel Alegre, Stephen Gulis Jr., Michael Harrison and Michael Peel. The female directors are Ibach, Brenda Lauderback, Barbara Matas, Kathleen Nedorostek, Vicki O'Meara and Kilpatrick.

Among other Minnesota public companies, Best Buy has reached near-gender parity on its board, with five of its 11 board seats held by women.