Light Bulb - Bankers

Q: How many bankers does it take to change a light bulb?
A: None, bankers don't change light bulbs.

Light Bulb - Post Doctoral Fellows

Q: How many post-doctoral fellows does it take to change a light bulb?
A: One, but it'll probably take three or four tries to get it right because he/she will probably give it to the technician to do.

Pentagon Officers to Change Lightbulb

Q: How many Pentagon procurement officers does it take to change a lightbulb?
A: Look, for only $87 billion, we can put up this chain of fluorescent satellites that will illuminate the whole planet.