Replies

No, it's not a "guesstimate," it's an approximation informed by random-sample testing of the general population.

Then answer me this:

1. What was the sample size?
2. How did they recruit sample participants?
3. How did they ensure their recruitment of sample participants was truly random?
4. What are the cross tabulation categories they examined?
5. Do those categories indicate higher risk of infection for certain types of people or certain sexual habits?
6. Did they account anywhere in their sampling for biases produced by the tendency of people to lie about their sexual habits?
7. Did they account anywhere in their sampling for biases produced by likely respondents? (Put another way, unless they forcibly pulled people off the street and tested them at random there probably aren't very many 12 year olds who volunteered for this study)
8. Did they pay the participants to take the study, and if so did this in any way bias the sample?
9. What was the timeframe of the survey? Was it done all at once or staggered to produce time series data?
10. Did they bother to provide any error or significance tests on their survey when it was done?

Since you are such an expert on this 80% figure and have posted it dozens upon dozens of times over the last few days, I am certain you will have little difficulty providing a source that answers all these questions.