That is just some number you came up with and it isn't accurate.
If you don't visit porn, then you don't have to filter for porn. A solution so simple that it is brilliant and orders of magnitude more effective than using multi-layered web content filtering.
I do a lot of really high risk surfing as part of my job, and I can tell you from firsthand experience that web content filtering adds next to nothing to overall protections.
Web content filtering is more important to the person's psychological state than to any really significant layer of protection.
People on the forums promote web content filtering but they don't know what they're talking about. That's what I am pointing out.
The worst are those that think somehow they will visit a website like MalwareTips, click on something, and then get re-directed to some webpage that looks like MT that unknowingly downloads and installs stuff in the background that will smash their system. There are so multiple layers of misunderstanding in such thinking.
Web content filtering is more likely to allow you to infect yourself than to save you. It's just not very effective. It is known for high false negatives. The disadvantages are numerous and high.