Last week, regulators in New York State said health care premiums for some consumers could drop by 50 percent or more next year, when insurers start competing for business under the new federal health law. Premiums for an individual policy in New York City could drop from $1,000 to $400 a month.

Other states aren’t seeing that sort of robust competition. The nation’s biggest health insurer, Minnetonka-based UnitedHealth, has said it simply won’t offer policies on some of the state insurance “exchanges.’’

Which raises one of the pressing questions behind the historic experiment known as Obamacare: Will insurance companies participate? Specifically, will consumers find attractive policies at competitive rates when the law’s online exchanges debut Oct. 1?

Early signs say the answer is yes, according to a study released last week by the Urban Institute, a respected think tank in Washington, D.C.

After surveying the action in six states, the authors wrote: “Our central conclusion is that there will be robust competition in many states, and this will lead to reasonably priced premiums.’’

Urban Institute scholars are tracking the rollout of the Affordable Care Act in 12 states, including Minnesota. Last week’s report focused on Oregon, New York, Rhode Island, Colorado, Maryland and Virginia.

Colorado, for example, expects nine insurers to offer coverage, with premiums for a midrange individual policy running $300 to $400 a month. (Similar coverage costs about $400 a month in Minnesota now.) Oregon expects 11 carriers, with premiums ranging from $221 to $486.

Minnesota was not included in this study. But the state Commerce Department says nine insurers have filed products for Minnesota’s exchange — known as MNsure — including Blue Cross, Medica, HealthPartners and UCare. Premiums aren’t public data yet.

Not that it’s been smooth sailing for the new law. The Urban Institute authors note that many states have worked hard to court insurers, granting them great flexibility in designing and pricing their policies. Insurers have their own set of worries: The United States has 49 million uninsured people, and no one really knows how many will apply for coverage and what sorts of health conditions they will bring to the marketplace.

“There is a general consensus that the first year will be somewhat chaotic,’’ the report notes. Which could be an understatement for the biggest experiment in social policy since Lyndon Johnson created Medicare and Medicaid.