What about the last couple percent?

I was washing my hands at work and I saw something interesting on the soap container.Ok, let's look closer...95% natural. What's the other 5%??If it wasn't printed on the bottle I wouldn't have given it a second thought. But since it's right there in my face it draws attention to it.Then I remembered that I saw something similar at home...My shampoo:94% biodegradable -- what of the last 6%? What happens with that?Same thing with the conditioner:92% with 8% somehow unaccounted for.Go figure.