Now, there is no shortage of explanations: Perhaps everyone just thought that if it was good enough for Bill Clinton and Monica Lewinsky, it was good enough for them. Moreover, as an economist, I feel uniquely qualified to opine on why it is happening. I am more than a decade away from being either and so regard myself as a neutral in this debate. In some quarters, that might be regarded as progress, but how you feel about it probably depends on whether you are a teenager or a parent of teenagers.