NEW YORK (CNN/Money) - Health insurance costs are going up, and up, and up. And in some cases, up some more.

Premiums for employer-sponsored plans rose by 11.2 percent in 2004 -- their fourth straight year of double-digit growth -- despite a modest pull back from 13.9 percent a year earlier, according to a study released Thursday by the Kaiser Family Foundation and the Health Research and Educational Trust.

Employees, on average, now kick in $558 of the $3,695 yearly cost of a single coverage plan and $2,661 of the $9,950 cost for family coverage. Last year they paid $508 and $2,412.

The percentage of premium costs paid by employees was about the same, at 16 percent for single coverage plans and 28 percent for family plans.

Overall inflation was 2.3 percent, according to the report, and the gain in wages was 2.2 percent.

"To paraphrase Everett Dirksen: A billion here, a billion there, and pretty soon you're talking about some real money," said Jon Gabel, vice president for health systems studies at HRET. "You put it together over four or five years than you can really see the dramatic change."

Since 2001, premiums for family coverage shot up by 59 percent compared to a 9.7 percent gain in inflation and a 12.3 percent wage growth rate.

The gaping hole between premium increases and wage gains in particular, Gabel says, makes for a lower standard of living as fewer people and businesses can afford coverage.

The numbers support his argument: The percent of those covered by employer-sponsored plans fell to 61 percent from 65 percent in 2001, leaving an estimated 5 million fewer jobs providing health insurance.

Still not sure if you are feeling the pinch? Here are some ways that employers are passing the bill.

• Higher co-payments. The percentage of workers paying a $20 co-payment for office visits has risen to 27 percent from 16 percent just one year earlier.
• Less drug money. Average drug co-payment costs have risen to $10 for generic prescriptions, $21 for preferred, and $33 for non-preferred.
• Bigger deductibles. Deductibles rose to $414 from $384 for conventional single coverage plans and to $861 from $785 for conventional family plans. HMOs, on average, increased their deductibles for single plans to $44 from $30 and to $80 from $65 on family coverage plans during the same period.

Next year's prognosis shows a continued push towards even greater employee responsibility in health care coverage.

According to the Kaiser survey, 52 percent of large firms (those with 200 or more workers) say they are "very likely" to boost employee contributions in the next year versus 15 percent of small firms.

Looking ahead to 2005 Forget generosity. Here's the percentage of large firms that are either "very likely" or "somewhat likely" to... Category Very likely Somewhat likely Increase employee deductibles 14% 38% Increase employee co-pays 14% 38% Restrict coverage eligibility 2% 7% Source: Kaiser and (HRET)

Employees at large firms may also pay more for prescriptions, as 18 percent of big companies say they are "very likely" to raise worker co-pay rates. Only 5 percent of small firms say they are "very likely" to consider such a move.

But smaller companies are more apt to say they are "very likely" to drop health coverage all together. Four percent of small firms (versus 1 percent of large firms) say they are "very likely" to discontinue carrying health insurance entirely. Overall, the number of small firms offering health insurance eased to 63 percent in 2004 versus 68 percent in 2001.

The report notes that small firms may have a particularly difficult time budgeting family coverage, which averages $9,950 a year for employers (modestly less than a year of minimum wage work) if premiums continue to grow at its recent pace.

The study surveyed 3,017 randomly selected public and private firms with three or more employees and was conducted January through May 2004. Kaiser and HRET have conducted the joint survey for six years.