New changes to U.S. Senate health-care legislation would significantly ease a requirement that individuals purchase insurance, but policy experts raised concerns Friday about whether it would fulfill the desired effect of making health coverage more affordable.

The bill, which Senate Finance Committee Chairman Max Baucus, D-Mont., hopes to bring up for a final vote in the panel next week, would issue financial penalties for people who don't purchase insurance.

Known as an "individual mandate," the requirement and penalties are intended to spur individuals to buy insurance. Lawmakers hope this would in turn create a larger pool of insured people and therefore ensure the viability of proposed new insurance market regulations requiring insurers to accept enrollees regardless of their health status.

But an amendment approved to the health-care bill late Thursday seeks to soften the impact of the mandate by lowering the highest possible penalty, from a top level of $950 to $750 a year. The penalty wouldn't apply at all until 2014, and it would gradually increase each year until it reached $750 in 2017.

The amendment, offered by Sens. Charles Schumer, D-N.Y., and Olympia Snowe, R-Maine, was approved by a 22-1 vote with only Sen. Jon Kyl, R-Ariz., dissenting.

The amendment also states that if the lowest cost plan available cost more than 8% of a person's income, that person would be exempt from the individual mandate. That cap - known as the hardship waiver - is lowered from 10% in the original version of the bill.

Agreement on the amendment came after negotiations between Schumer, who sought to lower the hardship waiver, and Snowe, who expressed concerns about the level of the penalties in the bill.

Schumer suggested that the changes were necessary because the committee was unable to increase the size of subsidies to purchase insurance. The best alternative, he suggested, is to make the mandate less onerous.

"If you have to make a choice when there are limited dollars, it seems to me this is the best choice," Schumer said.

A statement from Families USA, a group that advocates for greater access to health care, praised the Schumer-Snowe amendment, saying it would "insulate families from facing out of control premium costs."

But Edwin Park, a senior fellow at the liberal-leaning Center on Budget and Policy Priorities, suggested that the amendment would do little to increase the affordability of health insurance for low-income people. Lower-income people would still face the question of whether to purchase insurance that is only partially subsidized by the federal government or not carry insurance.

"The people who are now exempt from this mandate penalty are going to be uninsured, so they have no coverage at all," Park said. "The goal of health reform is to expand coverage."

Indeed, Schumer said Thursday that he had received estimates from the nonpartisan Congressional Budget Office stating that, over 10 years, roughly 2 million fewer people would have health insurance as a result of the lower threshold for the hardship waiver.

Also, some say it would have adverse effects on the insurance market as well. Paul Fronstin, a senior research associate with the Employee Benefits Research Institute, or EBRI, suggested that lower enforcement penalties for the mandate would cause more people to purchase insurance only when they are sick. EBRI is a nonpartisan, nonprofit research group funded by private companies.

"It may cause more problems then you're solving," said Fronstin. "If you're young and healthy, but you're expecting to have a baby, you wait until you're pregnant to buy insurance."

A group of people entering the insurance market that is both smaller and sicker could create problems for health insurers. The companies have agreed to an array of proposed new regulations in the insurance market, but only if a strong individual mandate guarantees a large pool of insured people.

But the overall effect on insurance pools may not be dramatic, according to Park. He pointed to a CBO estimate that, under the Baucus bill, the amount of uninsured would be reduced by 29 million people - a figure that puts the CBO estimate of how many would lose insurance under the Schumer-Snowe amendment into perspective.

"You're still getting a pretty sizable pool," Park said.

Still, insurers are raising warning flags, saying that a smaller number of people in the insurance rolls will raise costs throughout the health sector. Robert Zirkelbach, a spokesman for the America's Health Insurance Plans, or AHIP, trade group, said that it "increases the likelihood that premiums are going to increase for current policyholders."

Leading insurers in AHIP include Aetna Inc. (AET), Humana Inc. (HUM), Cigna Corp. (CI) and UnitedHealth Group Inc. (UNH).

-By Patrick Yoest, Dow Jones Newswires; 202-862-3554;