Two out of three homeowners in Pittsburgh would pay less in real estate taxes as a result of property reassessment, according to a University of Pittsburgh economist.

Chris Briem, a staff member at Pitt's University Center for Urban and Social Research, posted his conclusions today on-line.

His analysis looked only at new values for Pittsburgh residential properties that were briefly listed on the county's Office of Property Assessment Web site.

A spokesman for county Executive Rich Fitzgerald, a long-time opponent of reassessment, said he would review Mr. Briem's work. Mr. Fitzgerald ordered that the new assessment numbers be taken down and sent letters to Pittsburgh residents saying the county had certified 2002 base-year numbers for calculating this year's property taxes

The aggregate assessment number for 2012 -- covering all commercial and residential properties in Pittsburgh and Mount Oliver, which is part of the city school district -- rose 58 percent compared to the 2002 base-year values.

State anti-windfall laws require that taxing bodies -- school districts, municipalities and the county itself -- reduce millage rates proportionately to reflect the higher property values and head off any back-door tax increases.

The effect of the revenue neutrality requirement would result in 65 percent of residential properties in the city seeing a decrease in their total property tax burden, Mr. Briem found. Less than 25 percent of homeowners would see their taxes rise 10 percent or more under the new numbers, according to his calculations.

The neighborhoods where assessment increases are most concentrated include the South Side Flats, Lawrenceville, the Mexican War streets and portions of Highland Park and East Liberty. Many city and county officials have pointed to those neighborhoods as redevelopment success stories where new residents are moving in and real estate prices are rising, Mr. Briem wrote.

"Does anyone really disagree with dramatic price appreciation over a full decade" in those areas? he asked in his on-line posting.

Mr. Briem translated his findings into two city maps that can be viewed on his website. One shows each property facing a tax increase of 10 percent or more -- after millage rates are reduced -- as a green dot. While they are scattered throughout the city, they are more concentrated in the neighborhoods Mr. Briem identified.

Parcels where owners would see tax decreases are represented by red dots and they appear to cover most of the city.

Mr. Briem urged county and city officials to do their own studies of the tax consequences of the new assessment numbers.

"I would be glad to be proven wrong," he said in a phone interview today. "The county and the city should be able to do this analysis in a minimal amount of time."

The address for Mr. Briem's website is nullspace2.blogspot.com.