Out of curiosity I decided to do a little Googling. Since the legal definition of sodomy is "sexual intercourse involving anal or oral copulation," I don't think we have to ask what percentage of straight couples engage in oral sex.  I would estimate that number to be near 100%. Far more surprising to me was the percentage of straight people who have admitted to having anal sex. It seems 44% of straight men and 36% of straight women have had anal sex. With a total population of around 326 million, you do the math.