More than 12,000 Congressional staffers have signed up for coverage through DC Health Link. (Andrew Harrer/Bloomberg)

Thousands of people have purchased health coverage through the District of Columbia’s new small-business insurance marketplace, but only a tiny fraction of them actually own or work for a small business.

The rest are members of or work for a single large organization — Congress.

Starting this year, new rules require federal lawmakers and their staffers to enroll in health-care plans through the small-business exchange on the city’s new insurance marketplace, known as DC Health Link. So far, 12,359 representatives and staff members, including those who work in district offices across the country and those working on Capitol Hill, have purchased plans, according to numbers obtained by The Washington Post from city health officials.

Normally, the small-business exchanges are reserved for companies with fewer than 50 employees (rising to 100 workers over the next two years). Some lawmakers have therefore questioned whether it’s fair to allow elected officials and their staffs to access the new online insurance marketplaces, which are expected to offer relatively low-cost plans, when private companies the size of Congress are excluded.

During a hearing last year on the rollout of the exchanges, for instance, Sen. David Vitter (R-La.) called the rule a “special carve-out for Congress” and argued he should not get “completely different and better treatment” than other Americans under the law.

Others have complained that they were forced to switch from the Federal Employee Health Benefits Program, which is still used by other federal workers, to plans on DC Health Link. In part, that’s because the city’s online exchange, like many others across the country, experienced a number of technical problems during the first few months.

Mila Kofman, executive director of the DC Health Benefit Exchange Authority, says her team has ironed those out, as evidenced by the increasingly strong enrollment numbers.

“We were quite successful in enrolling more than 12,000 people who work for Congress, including those on the Hill and in district offices,” Kofman, said in an interview. “We worked just as hard to get them enrolled as everyone else.”

The congressional total represents 70 percent of the private insurance plans purchased so far in the District and 98 percent of the enrollment on the city’s small-business exchange.

Kofman noted that fewer than 300 actual small-business owners and employees have fully enrolled in coverage through DC Health Link, though a number of other small firms have selected plans but are still in the process of enrolling their employees.

Meanwhile, about 5,000 people have signed up through the city’s insurance marketplace for individuals and families, which Kofman says has been her team’s top priority. An additional 8,451 individuals have signed up for Medicaid through DC Health Link.

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