"We're looking at a composite of various markets, and each market is complex," he said of the effort to track individual premium rates. "Coming out with a single number is going to be fraught with over-simplification."
One trend in the data should have a calming effect on premium rates in the exchanges, Estupiñan said.
"In many of the insurance exchanges, some of the larger national players did not join. In many markets, there will be more of these kinds of new entrants [to the exchanges] in 2015," he said, adding these established healthcare payers are adopting a "conservative premium-setting approach."
In particular, the set of carriers that will be new to the exchanges in 2015 appears unlikely to try to under-cut HIX competitors with aggressively low premium rates, he added.
Premium rates only tell part of the story about 2015 HIX consumer costs and the business strategies of carriers operating on the exchanges, said Katherine Hempstead, team leader and senior program officer at the Princeton, NJ-based Robert Wood Johnson Foundation.