NEW ORLEANS  Years before Washington spent $787 billion on a national stimulus bill, it staged an unintended trial run in Louisiana, a huge injection of some $51 billion for which historians find few, if any, precedents in a single state.

The experiment is still playing out, but some indicators suggest that what occurred in Louisiana  dumping a large amount of reconstruction money into a confined space in the three and a half years since Hurricane Katrina  has had a positive outcome. The state’s unemployment rate of 5.7 percent in February was considerably below the national average of 8.1 percent, and it was the only state to see a drop in unemployment from December to January. It was also the only state with an increase in non-farm employment in February.

State economists specifically mention what one called “the ongoing building boom” from federal dollars as a main reason for the numbers. Largely a result of the damage caused by Hurricane Katrina, construction projects have not dried up as they have elsewhere, and a few can even be seen in downtown New Orleans.

Construction has “really hung in there and done very well,” said Loren Scott, an emeritus professor of economics at Louisiana State University. “In most states construction is way down, but in ours it has been up.” The relatively low unemployment rate in Louisiana “tells you that the stimulus can have an effect,” Mr. Scott said.