AUGUSTA - Gov. John Baldacci on Wednesday updated a re-election campaign claim that his economic plan is working by citing new Census Bureau data that, to the initial puzzlement of economic analysts within and outside his administration, showed Maine’s median household income growing by 5.5 percent from 2004 to 2005.

‘‘The U.S. Census numbers show that many people in Maine are finding opportunities to work and increase their earnings,’’ Baldacci said.

On Tuesday, as the Census Bureau released its findings, several administration officials said they were taken by surprise.

State Economist Catherine Reilly said the reported jump in median household income presented ‘‘a different picture than we’ve seen from other data.’’

Another expert, Professor Charles Colgan of the Muskie School of Public Service at the University of Southern Maine who serves as chairman of the Consensus Economic Forecasting Commission, said at first blush he would question ‘‘that big a change in that short a time period.’’

Calling the growth finding ‘‘unusual,’’ Colgan added, ‘‘it’s not what you would expect given overall growth in the economy for that period.’’

Not long ago, a report by the Federal Reserve Bank of Boston found that ‘‘New England’s northernmost state did little but tread water in 2005, as 2004’s mild growth came to a standstill.’’

It cited ‘‘lackluster’’ employment measures, ‘‘tepid’’ income growth, a cooling housing sector and a decline in the value of merchandise exports.
‘‘Maine’s recovery seems to have stalled,’’ the report said, adding that, ‘‘In fact, Maine was the only state in the country to see a decline over this period, except for Louisiana.’’

Ed Welniak, chief of the income surveys branch of the Census Bureau, said Wednesday the new report’s findings put Maine among seven states showing an increase, and that statistically none of the state increases could be said to be larger than another.

Baldacci said Wednesday his economic plan includes ‘‘investing in higher education, expanding research and development; expanding the reach of investments and incentives; enhancing renewable and alternative energy sources; and continuing tax relief efforts.’’