A noted sex therapist, aware that people often misreport their sexual frequency, devised a test to determine the truth. To validate his theory, he gathered a large audience in an auditorium. He proceeded down the line, asking each person to smile. Based on the breadth of their smiles, he accurately guessed each individual's frequency of sexual activity.
The last man in line was grinning from ear to ear.
"Twice a day," the therapist guessed. The man said no.
"Once a day, then?" Again, no.
"Twice a week?"
"No."
"Twice a month?"
"No."
Finally, the therapist asked, "Once a year?" The man said yes.
Frustrated that his theory had failed, the therapist demanded, "What the heck are you so happy about?"
The man replied, "Tonight's the night!"