How many economists does it take to change a light bulb? None. If it really needed changing, market forces would have caused it to happen.
How many tax advisors does it take to change a light bulb? "In the summer there is a tax deductible convention in Hawaii, dealing exactly with this issue."
How many accountants does it take to change a light bulb? Two, one to change the light bulb and one to check that it was done within the given budget.
How many bankers does it take to change a light bulb? Four. One to hold the bulb, and three to try and remember the combination.
How many stockbrokers does it take to change a light bulb? Two. One to take out the bulb and drop it, and the other to try and sell it before it crashes (knowing that it’s already burned out).