The Maine Real Estate & Development Association’s MEREDA Index, a semi-annual measure of the strength of Maine’s commercial real estate market, is down compared with the fall and spring of 2015, the association said Tuesday.

The MEREDA Index for spring 2016 is 91, compared with 100 in fall 2015 and 110 in spring 2015, the association said. Prior to that, the index, which was first published in spring 2013, had not topped 80, MEREDA said. An index score of 100 would be roughly equal to the market’s 2006 peak in terms of construction employment and the total value and square footage of properties sold.

MEREDA said in an news release that the index was unusually high during the two prior periods because of two huge commercial real estate deals in downtown Portland: the $35 million sale of 100 Middle St. in March 2015 and the $66 million sale of One and Two Portland Square in April 2015.

“The actual dip in commercial (real estate) exclusive of these very large sales was small,” said MEREDA President Michael O’Reilly, a senior vice president at Bangor Savings, in the release. “The residential component was a primary positive driver; sales of existing homes and new mortgage originations both saw strong increasing trends.”

The lack of available homes for sale is driving demand for new residential construction in both the single-family and condominium market, O’Reilly said.

While the construction industry continues to deal with a workforce shortage, the construction component of the index is exhibiting a gradual rise, he said.

“In fact, construction component of the MEREDA Index is now at its highest since 2008,” O’Reilly said.