They haven't talked about it in school?
So I started to explain that people are angry because of the growing divide between the rich and poor due, in part, to corruption of financial institutions and blah blah blah...
"OH! oh I think I know what you mean."
"Yeah. Remember when Grandma took me to open my savings account at Wells Fargo?"
"We put in $30 and then the next time that Grandma came to visit we went back to the bank to put in ten more dollars but there was only FIVE DOLLARS left!"
"Grandma was so mad and said it wasn't right and that I should be getting money: INTEREST. But the Banker told her it didn't work that way and there was a $10 fee every month the balance was below $100.... Is that what you mean by Occupy Wallstreet?"
Yup. He understands perfectly.