Though it must be said that the latter are cranks who are impossible to take seriously if you look into their claims - basically an MBA who went off the rail with conspiracy theories...
Not just cranks. There are quite a lot of choices as to how you calculate a price index and politics can easily enter in to which choice is taken. I'm not so up on the US index but the UK one tends to weight everyday stuff like the price of a loaf of bread in the supermarket but try coming to London and going to a trendy restaurant and staying in a nice hotel and you'll find those have gone up well above the official rate of inflation.
