Ken Gordon wrote:  
>The GDP, of course, measures value added. Sex, at least in the form  
>discussed here, involves two people each of whom has an imputed input  
>cost paid to the other. The value added by the transaction is zero.  
  
You might profit from reading George Reisman. "The Value of 'Final Products'  
Counts Only Itself," The American Journal of Economics and Sociology,  
Vol.63, No. 3(July 2004).  
  
Samuel Bostaph