The hell it didn't. It had a huge impact on our economy.
Every day, 3000 babies die, yet we increase our population by 3000 each day. The fact that on 9/11, 6000 died, and our population held constant for one day, did not have "any" effect on our economy,it is too small, and too little, to have any effect on our huge economy. People who blame the poor economy for the past 2 years on one single day where the population in the United States did not increase, are using it as an excuse. There are 280 million people in this county, we have 3000 abortions each day, we have 5000 births each day, we immigrate 57,000 new legal immigrants each week, and another illegal 50,000 come in each day.
3000 extra people dying on 9-11 did not hurt our economy any more than Pearl Harbor did in 1941, nor did D-Day in June of 1944 throw us into an economic depression, nor Gettysburg, nor the massacre of Custer in 1876, etc , etc.
Frankly, I would like to see those responsible for the 14 Saudis and the 3 others from the United Arab Emerites who DID blew up the WTC(not the Iraqis) and kill americans to be found and punsished.
In the final analysis, the war in Iraq was actually a detraction to the finding of those who did cause the WTC and pentagon killings.