Consumer-driven health plans (CDHPs) have surpassed health maintenance organizations to become the second most common plan design offered by U.S. employers, according to a survey.

Preferred provider organizations continue to be the most widely offered plans, with 79 percent of employers offering these plans in 2011. But Aon Hewitt’s survey of nearly 2,000 U.S. employers representing 20 million U.S. employees and their dependents found that 58 percent of employers offered a CDHP and 38 percent offered HMO plans.

Among employers that offer CDHPs, health savings accounts (HSA) outpace health reimbursement arrangements (HRA) by two to one (34 percent versus 18 percent). However, Aon Hewitt’s survey shows a higher number of employees enrolling in HRAs, with 43 percent of employees enrolling in HRAs compared with 28 percent in HSAs. Aon analysts said this reflects the fact that HRA plan designs are popular among large employers embarking on full replacement CDHP strategies, as they offer more design flexibility to the employer than HSA designs. HSAs, on the other hand, are typically offered as one of several plan options available for employees to choose between and therefore generate lower enrollments.

A growing number of employers are also considering using voluntary/elective benefits to supplement these plans, such as critical illness, hospital indemnity and accident insurance policies. Of those currently using this tactic, more than a quarter (26 percent) can attribute a significant-to-moderate increase in CDHP enrollment due to the availability of voluntary or supplemental medical benefits.

While just six percent of employers use voluntary/elective benefits today to complement the CDHP and encourage enrollment, 42 percent report they are considering this approach in the next few years, according to the survey.