I admit I don't have data on this topic, but only anecdotes. Four of my relatives have been teachers for teenage students in recent years. I am often genuinely shocked at the very common use by teens of what I was taught was vulgar and obscene language in everyday speech and texting on I-phones.
Maybe I should not be so surprised when once considers that teens often look to empty-head celebrities for role models such as those at the Golden Globe Awards this month who indulged themselves in an orgy of pointless vulgar speech. My point is that speech represents thought and the use of vulgar speech is often a sign of selfish disrespect for others.
But the really scary part of the problem is that when vulgar speech becomes so common, the teens actually do not even understand that the words are vulgar and that accelerates a downward spiral in the decline of culture. This is why adult supervision is so important and necessary.
If a teen uses dirty words, it is the duty of any adult who knows better to correct and educate the teen that such language is disrespectful and reflects badly on the family home of the teen. The hottest places in language Hell should be reserved for any teacher who also uses vulgar language to curry favor with students.
The use of vulgar language is really not funny in spite of one funny scene with Darren McGavin in Gene Shepherd's "A Christmas Story." The character of young Ralphie says that his father "worked in profanity the way that some artists work in oils or clay." But while that movie role showed a father cursing a flat tire or the neighbor's dogs, he was not cursing or trying to hurt or insult his children or others with vulgar language for its own sake.