We're approaching the 50th anniversary of the assassination of President John F. Kennedy, an event that wrenched this nation and spawned countless conspiracy theories. Was Kennedy killed by the Cubans? The CIA? The Mafia? The military-industrial complex? Time to spread your blanket on a grassy knoll and examine these 10 conspiracy theories:

1 Some Pakistanis doubt the story of Malala Yousafzai, the teenager who received worldwide support after she was shot and wounded by the Taliban for promoting the education of girls. Suspicion that she is a CIA plant or a greedy hoaxer is so common in Pakistan that a journalist there ridiculed doubters with a satirical piece revealing that Malala's "real name was Jane" and that the DNA in her earwax showed that she was "probably from Poland." But other media outlets missed the joke, citing the report as yet more evidence of the Malala plot.

2 Psychologists say the best predictor for someone believing a conspiracy theory is belief in other theories, even if they're contradictory. Researchers at the University of Kent in England found that survey respondents who believed that Osama bin Laden died long before the U.S. Navy SEAL attack in May 2011 were actually more likely to also agree with the theory that he was still alive.

3 The Illuminati was a Bavarian secret society founded by Adam Weishaupt in the late 18th century that was extinguished within a few years. Or was it? Conspiracy theorists believe the Illuminati remains alive and is bent on world conquest. It's certainly bent on domination of book lists, with Dan Brown's novels as best-sellers, and other authors offering such titles as "Hip-Hop Illuminati: How and Why the Illuminati Took Over Hip-Hop" and "Mary Todd Lincoln and the Illuminati." Then there's the video "Die America Die!: The Illuminati Plan to Murder America, Confiscate Its Wealth, and Make Red China Leader of the New World Order."

4 The struggling New York Knicks desperately needed the NBA's No. 1 draft pick in 1985, certain to be Georgetown's Patrick Ewing. But seven teams were in the running, with the draft order determined by Commissioner David Stern picking envelopes out of a bowl. When the Knicks won the top pick, the "Frozen Envelope Theory" was born. Some suspect that the Knicks' envelope was chilled so Stern could identify it by touch. Others think a corner of the envelope was bent for the same purpose. But no one has ever proved anything.

5 Conspiracy theories are big business. Alex Jones is an Austin, Texas-based talk radio host with millions of listeners over the airwaves and on the Internet who peddles apocalyptic tales of doom. He believes the U.S. government was behind the Oklahoma City bombing, the 9/11 attacks and the Boston Marathon bombings. As Jones spouts his dire warnings, his main advertising sponsor is a gold company called Midas Resources, which benefits from such hysteria as people seek out the traditional financial safety of precious metals. Midas Resources is owned by Ted Anderson, who also owns Genesis Communications — the network that carries Jones.

6 Did Marisa Tomei get the 1992 Academy Award for supporting actress by mistake when it was meant for Vanessa Redgrave? Some suspect so, despite no more evidence than the fact that Tomei was an underdog and that the award's presenter, Jack Palance, had behaved strangely at the show the year before. As Roger Ebert noted, accountants are poised in the wings to correct any error immediately, and there was only one name on the card that Palance read, so a mistake was unlikely. Chief purveyor of the theory is critic Rex Reed, whose credibility is not gold standard. (Reed was criticized for calling actress Melissa McCarthy "tractor-sized" and for panning the film "V/H/S/2" when he had watched about 20 minutes of it, among other transgressions.)

7 A "false flag" operation occurs when a group or country conducts an attack that is then blamed on another group or country. The burning of Germany's parliament building in 1933 was blamed on communists, providing justification for a Nazi crackdown. Historians are split on whether the Nazis actually torched the building or just took advantage afterward. But there's no doubt about a Nazi false flag operation six years later: A German radio station was attacked by Nazis dressed in Polish uniforms, a raid cited by Adolf Hitler as one reason for the invasion of Poland, which set off World War II.

8 Denver International Airport, which opened in 1995, is an epicenter for conspiracy theories. Depending on whom you believe, DIA houses a base for UFOs, vast bunkers to protect the elite during the apocalypse, an alien-run concentration camp or a temple to Freemasons and the New World Order. Theorists cite alleged clues, such as murals that depict environmental disaster and other world tumult, plus a reference to the New World Airport Commission. (A co-chair of the now-defunct commission thinks the name may have come from Dvorak's "New World Symphony.")

9 So what about JFK? Belief that multiple people conspired to kill the president in Dallas remains persistently high. In March 2001, a Gallup poll found 81 percent backed a conspiracy theory. In 2003, that number dropped to 75 percent, and in April of this year it dropped to 59 percent. So when was belief in conspiracy theories at its lowest? Interestingly, that came in the period right after the actual event, when 51 percent didn't believe Lee Harvey Oswald acted alone.

10 "Occam's Razor" is a principle attributed to 14th-century friar William of Ockham. It states that when there are a variety of explanations, the simplest one is often the correct one. But a conspiracy theorist might respond: That's what they want you to think.

Mark Jacob is a deputy metro editor at the Tribune; Stephan Benzkofer is the newspaper's weekend editor.

mjacob@tribune.com

sbenzkofer@tribune.com

SOURCES: "Conspiracy Films" by Barna William Donovan; "Religion of Fear" by Jason C. Bivins; "New York Knicks: The Complete Illustrated History" by Alan Hahn; "Dead and Alive: Beliefs in Contradictory Conspiracy Theories" by Michael J. Wood, Karen M. Douglas and Robbie M. Sutton; Texas Monthly; New York magazine; Gallup News Service; USA Today; rogerebert.com; insider.espn.go.com; news.discovery.com; westword.com; worldcat.org; dawn.com; The Washington Post; London Telegraph