Several lines saw an uptick in migration to a voluntary benefit, and almost all lines were more frequently offered as a voluntary benefit in 2013 compared with 2009. There was only one exception: short-term disability policies.

In 2009, only 11 percent of employers offered voluntary vision coverage. By 2013, that number has nearly doubled, to 20 percent.

Other lines also showed substantial voluntary migration rates: In 2009, 30 percent of employers offered voluntary critical illness policies; by 2013, 40 percent of employers were doing the same.

And the rate of voluntary cancer policy adoption jumped from 51 to 60 percent in that four-year period.

Landry and her team expected these results. What they didn't anticipate was the growing number of employers who cover 100 percent of supplemental policy premiums.

"[With the shifts to voluntary], there was migration in both directions," Landry said. "We weren't predicting that more employers would begin paying 100 percent of some of those lines that are traditionally thought of as voluntary offerings."

Accident policies were the most frequently employer-paid supplemental plans: In 2009, only 13 percent of employers paid 100 percent of accident coverage premiums; by 2013, it was 22 percent.

More employers are also willing to pick up the tab on vision premiums – those policies that also saw the swiftest migration to pure voluntary. By 2013, nearly one-quarter of employers were contributing 100 percent of the premium cost, up slightly from 2009. And 26 percent of employers paid all participants' dental premiums – a jump from 20 percent in 2009.

Source: LIMRA

Diagnosing employers' thinking

Economics is the best explanation for the unexpected uptick in employers taking fiscal responsibility for accident, vision dental and group life, said Landry.

In 2009, the country was deep in the throes of recession. "It was a bad time for the benefits market," said Landry – a time when employers tried to contain costs by eliminating the investment in workers' benefits.

The ensuing economic recovery and improved unemployment rate, of course, encouraged employers to once again loosen the purse strings. Hence the subsequent growth of the voluntary market.

"Employers have budgets they have to stick to, and that means they have to make trade offs," said Landry. The average employer's all-in benefits cost equates to around one-third of each employee's salary, Landry added, according to LIMRA research.

But more employers remain invested in offering as comprehensive of a benefits suite as possible. This is evidenced by the very fact that more employers are covering more of the types of benefits that were once offered only on a voluntary basis – even though many participants may be blind to the true cost of these perks.

"[Employers are] cognizant of their employees' needs, and their own need for a healthy workforce," said Landry.

Most lines are also offered on a contributory basis – one in which employers and participants share the premium cost – said LIMRA, in most instances at an even greater rate than their migration to employer-paid and voluntary bases.

That reality should bear out next year, said Landry, when LIMRA will update its research on the movement of benefits toward the voluntary column.

Employers will continue to struggle with offering a rich benefits package while combating major medical inflation – an inevitable balancing act. But some benefits may make more financial sense as voluntary offerings, depending on cost. Landry cited vision as an example — a highly valued benefit to employees and an affordable alternative to other voluntary products. Employers, then, can make vision available purely on a voluntary basis without placing undue strain on their workers' pocketbooks.

In other cases, employers may choose to offer a benefit contribution — particularly for a line of coverage they want to encourage employees to elect, said Landry.

"The evidence shows that when employers offer to pay some of the premium, more participants will buy in," she said. "The downside to shifting a policy to a completely voluntary offering is that it tends to lower participation rates."

In most cases, when an employer does pay part of a premium —57 percent of employers paid between 10 and 90 percent of vision premiums in 2013, for instance — they can be less than forthcoming about the total of their portion of the bill.

"It's not about hiding the cost split," Landry said. "Employers just have a limited amount of space and time to communicate the value of a benefit and how to go about enrolling in it. They have to prioritize their messaging."

Change is difficult

Employers still struggle to engage employees during enrollment seasons, concluded Landry and other analysts.

"The general consensus among researchers is that people recognize the value of insurance, but they are unsure of how much and what kind they should have," said Landry.

It can be a considerable challenge just to motivate employees to read and learn about their benefits choices, Landry said, seeing as how participants spend limited time understanding an often overwhelming array of options come open enrollment.

This is why participants usually select the same benefits year after year.

"Change is difficult," said Landry, "especially when newer products like critical illness and accident policies are offered. Unless information is clear and easy to digest, participants are likely to lose interest."

And that just compounds their uncertainty – making it even harder for participants to make a decision.