In 1999 355,000 Americans said they did this once per week?

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Clarification of Question by zcsccg1-ga on 10 Oct 2002 09:26 PDT

The question implies that its something that is done weekly by an
individual, so its not something like getting hit by a truck or having
a heart transplant .... (I did some searching and came up the heart
bypass surgery answer but its only something a person can have done
once, i assume)

This could be anything from, well, taking a bath, having s**, to
brushing teeth, etc.
One will never know the answer unless one finds the original "study".