Light Bulb - Russian Leaders

Q: How many Russian leaders does it take to change a light bulb?
A: None, the old bulb is just suffering from a cold.

Psychiatrists to Screw in a Light Bulb

Q: How many psychiatrists does it take to screw in a light bulb?
A: One, but it takes five sessions.

Dino Convo

Dinosaur #1: "How many economists does it take to screw in a light bulb?"
Dinosaur #2: "What is an economist?"
Dinosaur #1: "A flunkie mathematician who tries to predict the population of kangaroos in Australia. But that's not important and don't ask what a Kangaroo is."
Dinosaur #2: "I don't know, how many?"
Dinosaur #1: "10 economists and one grad student. One economist to make a model, one to run the regression, one to test the hypothesis, one to interpret the results, one to conclude how to screw it on, one grad student to screw it on, and five economists trying to fight off the dinosaurs trying to eat them.