Why women talk more than men?

A husband was trying to prove to his wife that women talk more than men.
He showed her a study which indicated that men use about 10,000 words per day, whereas women use 20,000 words per day.
The wife thought about this for a while.
She then told her husband that women use twice as many words as men because they have to repeat everything they say. 
Her husband looked stunned.  He said "What?"