two large garbage bags

Some may have seen or heard this one before:

A little old lady was walking down the street dragging
two large plastic garbage bags behind her. One of the bags rips
and every once in a while a $20 bill falls out onto the sidewalk.

Noticing this, a policeman stops her, and says,
"Ma'am, there are $20 bills falling out of your bag."

"Oh, really? Darn!" said the little old lady. "I'd
better go back, and see if I can find them. Thanks for telling me."

"Well, now, not so fast," says the cop. "How did you
get all that money? "You didn't steal it, did you?"

"Oh, no", said the little old lady. "You see, my back
yard is right next to the football stadium parking lot. On game
days, a lot of fans come and pee through the fence into my flower garden.
So, I stand behind the fence with my hedge clippers. Each time
some guy sticks his thing through the fence, I say, '$20 or off it comes'.

"Well, that seems only fair" laughs the cop. "OK. Good
luck! Oh, by the way, what's in the other bag?"

"Well, you know, not everybody pays".