"Inquiry" joke

(This is from a little book called "Buurmans hemd nader bekeken," by
Harry de Jong (in Dutch). I thought it deserved a bigger audience.
Hans)
"How often a week do you sleep with your wife?"
asked the inquirer.
"Three times," I said without hesitation.
"That is once more often than your neighbour,"
the inquirer said, writing.
"That makes sense," I said, "after all, she's my wife."
Hans Buurman, Pattern Recognition Group
Faculty of Applied Physics, Delft University of Technology