The percentage of eligible departing workers who choose to pay for health coverage continuation benefits is staying high despite the expiration of a temporary federal subsidy.

The take-up rate for Consolidated (COBRA) Omnibus Budget Reconciliation Act continuation benefits now stands at 21%, up from an average take-up rate of 12% before Congress created the temporary subsidy in March 2009, according to Hewitt Associates Inc., Lincolnshire, Ill. (NYSE:HEW).

Hewitt has based those figures on an analysis of COBRA enrollment data for all workers who gave left their jobs since 2004. The database included information about 200 large U.S. employers with a total of 8 million employees.

The Senate let the COBRA subsidy expire in July.

When the subsidy program was in effect, involuntarily terminated workers paid 35% of the premiums, the federal government paid 65%, and employers and insurers covered the administrative costs.

Before the subsidy was created, any eligible worker who wanted to take up COBRA had to pay an amount equal to 102% of the cost of the premiums. The government did not distinguish between workers who left voluntarily and those who left as a result of layoffs or other involuntary terminations.

The cost of COBRA coverage is now equal to 102% of the cost of premiums for all eligible, departing employees.

The cost of 102% of the premiums averages about $8,800 per year.

When Hewitt looked only at the subset of workers who were involuntarily terminated and eligible for the COBRA subsidy, Hewitt found an average monthly take-up rate of 38%, with the take-up rate peaking at

46% in June 2009.

In May 2010 — the last month that the subsidy was available — 31% of involuntarily terminated workers were enrolled in COBRA, Hewitt says.

“With the unemployment rate close to 10%, more Americans have to turn to COBRA as a way to access health insurance, especially for workers who are involuntarily terminated and either don’t have a new job right away or don’t have a job with an employer-provided health plan,” says Karen Frost, a Hewitt’s health and welfare outsourcing expert. “However, enrollment rates will likely decline over time, as workers can’t–or aren’t willing to–afford the high premiums associated with COBRA coverage.”

Workers who enrolled in June expecting the subsidy would be extended may later drop coverage when it becomes clear that the government won’t help pay for the cost of continuing health coverage, Frost says.