How many studies will we need before we see pyrethrin/permethrin as ineffective with head lice?

These are the related pesticides in products such as Nix and R&C.  I don't know how many studies we will need before our health professionals stop recommending these products but here's another one. It basically says that almost all North American lice have developed a genetic resistance to this pesticide.  Please, please, please don't waste your money on it. The effectiveness quoted in the pamphlets of these products was true when they first came out in the 1980s but our overuse of these products have made them almost useless now.  The last line of this study's abstract says, "Alternative approaches to treatment of head lice infestations are critically needed." Enough said.