A national survey of 811 adult residents of the United States conducted by Scripps and Ohio University found that more than a third believe in a broad smorgasbord of conspiracy theories including the attacks, international plots to rig oil prices, the plot to assassinate President John F. Kennedy in 1963 and the government's knowledge of intelligent life from other worlds.
The high percentage is a manifestation, some say, of an American public that increasingly distrusts the federal government.
"You wouldn't have gotten these numbers a year or two after the attacks themselves," said University of Florida law professor Mark Fenster. "You've got an increasingly disaffected public that is unhappy with the administration."
Fenster, author of the book "Conspiracy Theories: Secrecy and Power in American Culture," attributed the high percentage in part to the findings of the National Commission on Terrorist Attacks upon the United States (also called the 9/11 Commission), which concluded federal officials failed to prevent the attacks, but did not have specific knowledge of the date of the attacks.
An earlier Scripps Howard/Ohio University survey, conducted in July 2006, revealed that more than one-third of Americans thought federal officials assisted in the 9/11 attacks or took no action to stop them so the United States could go to war in the Middle East.
"What (the recent survey) could mean is that people are thinking that the Bush administration is incompetent, that there were warnings out there and they chose to put their attention on other things," Fenster said.