One word - CPI
In 1974 the average weekly income was $133, 20 years later in 1994 it rose to $658. Now in 2014 it is $1516 (I'm sure Miners get paid a lot more than this). So if wages have more than doubled in 20 years, along with the cost of living for everything (In 1994 Petrol was 60 cents/L) then it is safe to say that the Iron Ore should also rise accordingly.
