Of course, immediately I want to add - rating drivers "within their system" brings other complications. "The Schumacher case". What do I mean? It is often mentioned that he had a "weak era". If in, say, 2001 his closest championship rivals were Coulthard, Barrichello and his brother, this claim has an actual point. But really - this claim applies to cross-era comparison. So how to compare different eras? All this while we have enough trouble rating drivers already within their own era.