House Democrats unveiled a sweeping health care reform bill last Thursday built on shared responsibility.

Individuals would have to buy health insurance for themselves and their families.

Taxpayers would subsidize coverage for those unable to afford it on their own.

Employers would have to offer health benefits to their workers or make payments to help underwrite the cost of their coverage.

Most Americans get health insurance through their jobs. But that system has begun to unravel as health insurance premiums have soared. The cost of family coverage jumped 131 percent over the past 10 years.

A new report from the state Department of Social Services, which runs Missouri Medicaid, illustrates just how messy the current system has become.

The report ranked large companies with the most employees or family members enrolled in Medicaid. It's a big list — 172 companies.

Nearly 871,000 Missourians get health care through Medicaid. Workers at those 172 large companies account for just one in every 15, about 57,000 people.

But they represent a substantial expense to state and federal taxpayers. Their care cost taxpayers almost $27 million during the first three months of 2009.

The report lists only companies with at least 150 workers and at least 50 workers or their family members on Medicaid. The largest of them is Wal-Mart, which employs nearly 39,000 people in Missouri. About 4,600 of its workers or their family members are on Medicaid. Their care cost more than $4.2 million from January to March.

Another retailer, Casey's General Store, was number two. It employs about 3,500 people. More than 1,000 of its workers or their family members are on Medicaid. Their care cost taxpayers about $884,000.

That's not surprising. Most large companies offer health insurance to their workers. But the numbers vary dramatically by the workers' earnings, whether they work full or part time and the category of industry of their employer. In the retail industry, only about half of workers are offered coverage.

At companies that employ a large number of workers earning less than $23,000 a year, only about 40 percent are offered benefits. At companies with a substantial number of part-time employees, only a third of the workers get health insurance.

That pattern is common in retail stores, which is why a number of large retailers made the list. It's also true for temporary staffing agencies, call centers, nursing homes and home-care agencies, all of which rely on part-time, low-wage or temporary workers.

State government made the list, too. Missouri employs more than 59,000 people. About 1,000 of them have Medicaid coverage for themselves or family members at a cost of more than $800,000. Also on the list were large hospitals that employ thousands of people. They get much of their revenue from Medicare and Medicaid.

Large companies face the vexing challenge of trying to retain employees or create jobs in the face of a recession and rising health care costs. That makes it harder for them to cover health insurance expenses for part-time or low-wage workers.

Companies shouldn't be discouraged from hiring unskilled or part-time workers. Jobs, even those that pay low wages, keep the economy moving and families afloat.

The challenge for health reformers is to strike a responsible balance for all parties without crashing the whole system. Shared responsibility is critical.