Opponents of Obamacare have warned nearly since its inception that implementing the policy would prompt sharp increases in Americans' health care premiums. A new independent report suggests that premiums will actually be lower than the government expected. Oh, unless you live in Burlington, Vermont.

The idea that rates would spike — "rate shock," in the political parlance — is perhaps the best argument against the policy. In July, House Speaker John Boehner wrote about the possible increase in his home state of Ohio, which, he said, is "consistent with a nationwide report on 'rate shock' by the House Energy and Commerce Committee." That report, from the Republican members of the committee, suggested that "Obamacare will significantly increase premiums," and that "[b]oth opponents and supporters of the law have come to this conclusion." It cited, among the sources of its claims, analysis from the non-partisan Congressional Budget Office. That analysis is nuanced, but, yes, shows increases.

On Thursday, independent analysis conducted in 18 cities by the Kaiser Family Foundation offered advocates of the new law some good news: Those CBO estimates were almost universally too high. The foundation's core discovery?

[W]e estimate that the latest projections from the Congressional Budget Office imply that the premium for a 40-year-old in the second lowest cost silver plan would average $320 per month nationally. Fifteen of the eighteen rating areas we examined have premiums below this level, suggesting that the cost of coverage for consumers and the federal budgetary cost for tax credits will be lower than anticipated.

In fact, for that 40 year-old, a single person who makes just under $29,000 a year (250 percent of the poverty level), the average savings in the 18 cities would be about $45 a month. We took the data provided by the Kaiser Family Foundation (and its subsidy calculator, which gets its estimates from the original CBO estimates) and figured out how single people in each of the three age ranges Kaiser looked at would fare in the 18 cities.

First, the top-line numbers. Using the Kaiser calculator, we figured out premium cost predictions from the CBO and compared to each city.

Single 40 year-old
Cities where costs will be lower than CBO estimates: 15
Average monthly savings: $45
Most expensive city: Burlington, VT
Cheapest city: Portland, OR

Single 25 year-old
Cities where costs will be lower than CBO estimates: 15
Average monthly savings: $26
Most expensive city: Burlington, VT
Cheapest city: Portland, OR

Single 60 year-old
Cities where costs will be lower than CBO estimates: 17
Average monthly savings: $145
Most expensive city: Hartford, CT
Cheapest city: Burlington, VT

Got that, 59 year olds? It's finally safe to move to Vermont.

Then we went a step further. We created a table that shows premium rate changes form the CBO's estimates in each of the 18 cities for each of the three age groups. If the number is negative, that's how much lower than the estimate the foundation found the city to be.

City 25 year-old 40 year-old 60 year-old
Los Angeles, CA $-53 $-66 $-142
Denver, CO $-57 $-71 $-152
Hartford, CT $6 $7 $14
Washington, DC $-73 $-79 $-162
Indianapolis, IN $-21 $-26 $-57
Baltimore, MD $-74 $-93 $-199
Portland, ME $-21 $-26 $-57
Billings, MT $-50 $-63 $-135
Omaha, NE $-40 $-50 $-107
Albuquerque, NM $-86 $-109 $-233
New York, NY $138 $69 $-293
Cleveland, OH $-57 $-72 $-154
Portland, OR $-95 $-120 $-256
Providence, RI $-23 $-28 $-61
Sioux Falls, SD $-46 $-57 $-122
Richmond, VA $-54 $-68 $-146
Burlington, VT $161 $92 $-270
Seattle, WA $-31 $-38 $-82

And now the other caveats. These rate changes are based solely on that single person making $29,000 a year. Clearly, there's a lot of variability depending on where you live and how old you are. Start mixing in other data like salary, if you smoke, the number of kids you have, and the calculations get enormously complex. The second caveat is that it isn't immediately clear if the reductions found by the Kaiser Family Foundation are enough to mean an overall reduction in costs for health care recipients in the cheapest cities. Finally, this is only for the "silver" level plan, without subsidies. "Bronze" (read: "worse") plans are cheaper still, and have different fluctuations.

But given the amount of attention paid to the issue, it should be no surprise that advocates of the program are lifting up this report as a beacon of hope. And people in Portland, Oregon — among the cheapest cities in every age group — should be excited, too.

Photo: A single Portland man, aged 40 or so, with friend. (AP)